How to Quickly Replace A Cars Head Gasket (In 5 Hours)

In this last post we covered replacing a cars piston rings. But, in this post we’ll run through replacing a head gasket.

Why? Because, to replace piston rings, you need to remove the cylinder head.

But, to access the cylinder head, you must first remove the “cylinder head gasket”.

A bearded mechanic wearing a cap and glasses holds up a used head gasket in his right hand inside a workshop. The mechanic is standing near a white vehicle with its hood open, and various tools and equipment are visible in the background. The mechanic wears a navy blue t-shirt with the word 'Garage' printed on it, and the environment is brightly lit with a clean, organised workshop setting

The car I carried out the repair on was a 2014 Mazda Cx-5 SkyActive 2.2 Diesel.

And while it made sense to only “briefly” touch on this topic in the last post. It lined up the perfect opportunity to cover head gaskets, in full detail today.

So here’s what we’ll cover.



Diagram of a blown head gasket showing various types of leaks. The image highlights seven potential leak points: 1. Oil leak to outside, 2. Coolant leak to outside, 3. Compression leak to crankcase, 4. Leak between coolant and oil, 5. Compression leak between cylinders, 6. Compression leak to coolant, and 7. Compression leak to outside. The diagram shows the head gasket's position relative to the cylinders, and areas where blue and black sections indicate possible leak paths.

Can a car still drive with a Failed head Gasket?

The short answer is YES! Some cars will, and most certainly still can, but should never be, driven with a blown head gasket. Although, how the car will drive, is likely with many faults.

So never rule out the possibility of a head gasket failure because a car can “technically drive”. As it simply depends on, where?, and how?, the gasket has blown.

That being said, if you suspect a head gasket to be the issue. Then immediately stop the car, call a recovery service, and prevent the possibility of further damage being caused to the engine.

However, “suspecting” without testing will never suffice. Which is why professionals follow a precise process when diagnosing the symptoms of a failed head gasket.

Once the diagnosis has confirmed that a head gasket is the issue, you can then begin to remove the components preventing access to the problem area.

Please Read!

The following section specifically helps with diagnosing a failed head gasket.

However, if you’re already certain that the gasket is blown, then you can skip ahead to start making the repair.


This image is of a mechanic in a blue jumpsuit (in a garage) inspecting a car engine with a magnifying glass. The engine is partially disassembled, showing components like pistons and belts. The garage background includes various tools, and the scene has warm lighting, creating a workshop atmosphere.

How to Accurately Diagnose a failed Head Gasket

A failed head gasket can be found in a in a number of ways. Which is down to the fact that ‘the gasket can blow in a number of ways’.

A few of these ways include; general wear, overheating, loose head bolts, turbo over-boosting, faulty thermostats, pre-ignition or detonation, etc. 

However, the method used for testing should always be determined by current symptoms. Because, how you would approach overheating situation is totally different to the approach you would take for a non starting engine.

And in some cases, you might see no symptoms. Which is why it’s paramount to carry out thorough testing before starting repairs.  

Visual examples: Causes & Symptoms of head gasket Failure

The following images will provide examples of the types of symptoms that each failure can present. 

Understanding this will help you to decide on the appropriate test to carry out before starting the repair.

In the  diagram, the red circles represent the cylinders, while the green areas indicate the water jackets. A blue label marks the point of leakage between a cylinder and a water jacket. This failure occurs when the gasket breaks between the coolant passage and the combustion chamber. 

As a result, coolant enters the combustion chamber, causing excessive white exhaust smoke with a sweet smell—a common sign of coolant being burned in the engine.
This image illustrates a head gasket failure where the gasket has failed between the coolant passage and the exterior of the engine. Green-colored areas highlight the water jacket passages through which coolant flows. A leak is marked on the lower part of the gasket, showing where coolant is escaping from the water jacket to the outside of the engine. The problem leads to visible coolant leakage from the side of the engine, and the diagram emphasises the affected areas using a red arrow for focus and a label explaining the problem.
This image demonstrates a head gasket failure where the gasket has failed between a coolant passage (marked in green) and an oil passage (marked in orange). The leak is highlighted near the top of the gasket, where the coolant and oil paths meet, leading to contamination. This issue causes a milky consistency to appear in the oil filler cap or coolant reservoir, indicating that the coolant is mixing with the oil. A red arrow emphasises the problem, and the description explains the specific nature of the gasket failure in text.
This image shows a head gasket failure between two cylinders, marked in red. The leak between the cylinders is highlighted, indicating that the gasket has failed in that area. This type of failure leads to engine misfires and a loss of power output. The red arrow draws attention to the issue, and the accompanying text explains the problem and its symptoms.
The image illustrates a head gasket failure between an oil passage (marked in orange) and the exterior of the engine. The leak is highlighted at the bottom, showing where oil is escaping from the oil passage to the outside environment. This results in oil leaking from the side of the engine, known as an exterior oil leak. The red arrow emphasises the location of the problem, and the text describes the issue and its symptoms.

Fault Diagnosis: Understanding the symptoms

The table below consists of the most common symptoms of a head gasket failure. 

Each section will additionally provide the suggested checks that can be made to identify how and where the gasket has blown.

Reason

Coolant or oil is entering the engines combustion chamber and being burned

How To Identify Fault

Visually inspect exhaust smoke with engine running

Other Possible Causes

Faulty turbocharger, damaged piston rings, bad valve seals, or damaged cylinder walls

Reason

Gasket has blown between oil and water jacket passages in the engine

How To Identify Fault

Remove engine oil filler cap and inspect

Other Possible Causes

Build up of condensation in engine, cracked engine block, or oil cooler failure

Reason

Gasket has blown between combustion chamber and coolant jacket in engine. Combustion gases are entering the coolant system.

How To Identify Fault

Inspect coolant in reservoir while engine is running

Other Possible Causes

Air trapped in cooling system, clogged radiator, or faulty radiator cap

Reason

Oil or coolant is being burned in the engine, dissipating without leaks

How To Identify Fault

Run engine an inspect exhaust gases for unusual smells or smoke

Other Possible Causes

Evaporating coolant from a hot engine, small undetected leaks in hoses or radiator

Reason

Gasket has blown between oil or coolant passage and edge of the engines mating surface

How To Identify Fault

Inspect the engine and ground for visible signs of leaks

Other Possible Causes

Cracked oil pan, loose oil filter, or damaged hoses

Reason

One or more cylinders in the engine is not operating correctly

How To Identify Fault

Listen for rough idle, unusual engine sounds, or run diagnostic scan

Other Possible Causes

Faulty spark plug(s), ignition coil(s), or bad fuel injector(s)

Reason

Coolant loss or air pockets preventing heater core from receiving hot coolant

How To Identify Fault

Check if the heater blows cold air even with the engine at operating temperature

Other Possible Causes

Faulty thermostat, radiator, or water pump

Reason

Gasket is blown between the combustion chamber and the coolant passages.

How To Identify Fault

Check if in car heating blows cold while engine is at operating temperature (roughly 90°)

Other Possible Causes

Faulty heater core, stuck thermostat, or clogged heater hoses

Reason

Gasket has failed between cylinders resulting in a loss of pressure

How To Identify Fault

Perform a compression test with a gauge

Other Possible Causes

Faulty piston rings, cylinder walls, valves, or fuel injector clamp. Or engine is cracked

Reason

Engine ECU has detected a fault in one or more cylinders. May result in limp mode

How To Identify Fault

Run diagnostics test with OBD scanner

Other Possible Causes

O2 sensor failure, mass airflow sensor issue, catalytic converter problems, turbo failure

Reason

Coolant is entering the engines combustion chamber and being burned

How To Identify Fault

Start engine. Then, open oil filler cap to confirm steam is coming from inside the engine

Other Possible Causes

Radiator or hose leak, or faulty thermostat

Reason

Coolant is mixing in combustion chamber and being burned

How To Identify Fault

Stand behind car with engine running and smell

Other Possible Causes

Leaking coolant hoses, faulty radiator, or faulty heater core

Tests you can run to Confirm the gasket is blown

The following table contains a list of the tests that can be carried out to identify the type of failure the engine has. 

Additionally, you should now be able to read the symptoms and determine the appropriate test that should be carried out to confirm the fault.

Test NameTest Description Time To Carry Out Experience LevelProcess Video Link
Chemical Block Tester Detects if there is exhaust gases in the coolant system 15 minutes Beginner Fill test tube with solution. attach to coolant reservoir. Start car. Squeeze test pump. Check if solution changes colour. Watch here
Compression TestMeasures the level of compression being generated in cylinder(s)30–60 minutesIntermediate levelRemove spark or glow plugs. Mount test hose with gauge. Crank engine and take results. Watch here
Leak-Down TestIdentifies if there are leaks or a loss of pressure in cylinder(s)45–90 minutesProfessional levelMount tester to spark or glow plug hole. Increase air supply (100 PSI), then check gauge for leaks. Watch here
Coolant Pressure TestIdentifies leaks in the cooling system20–30 minutesBeginner levelAttach tester to coolant reservoir, then pump to 15 PSI. Check gauge and hoses for leaks. Watch here
Oil AnalysisDetects contamination of oil with coolant5–10 minutes (sample collection); lab testing: 2–3 daysBeginner levelExtract about 50ml of oil from engine. Send sample to lab for analysis. Watch here
Exhaust Gas AnalyserIdentifies if exhaust gas (e.g., CO2) is entering the coolant system20–30 minutesProfessional levelAttach tester to exhaust, then read on screen data. Watch here
Visual InspectionIdentifies visible signs of leaks, contamination, or wear in the engine and coolant system15–30 minutesBeginner levelVisually inspect in and around the vehicle N/a
Chemical Dye Test (UV Dye Test)Detects external leaks in the coolant system 30–60 minutesIntermediate levelAdd solution to coolant reservoir. Run engine for 15 mins. Inspect with UV light for leaks. Watch here
Boiling Coolant Test Identifies overheating issues via the cooling system15–20 minutesBeginner levelRun engine to normal operating temperature. Then inspect coolant in reservoir Watch here
Infrared Thermography (Thermal Imaging)Identifies abnormal temperatures in particular areas of the engine30–45 minutesProfessional levelUse thermal camera with engine running to see hotspots on engine. Watch Here
Vacuum Leak TestMeasures fluctuations in vacuum pressure, indicating a loss of compression.20–30 minutesProfessional levelAttach a vacuum gauge problem area, then pump, and check gauge.Watch here
Road Test Identifies unusual engine performance10–30 minutes Beginner levelDrive car uphill, at high speed, under high load. Review performance. N/a


This image of os a mechanic using a wrench to remove the head gasket from a car engine. The engine is partially disassembled, showing components like valve springs and rocker arms. The text 'HEAD GASKET REMOVAL @PistonTribe' is overlaid on the image. The background shows various engine parts and wiring.

A Step-by-Step Guide to Replace the Head Gasket On A Car

The following sections in this post will provide you with a comprehensive guide on:

  • Removing the cylinder head and its associated
  • Correctly cleaning the engine
  • Inspecting the engine and other relevant components
  • Replacing the head gasket
  • Reassembling the engine
  • Then, Testing the engine once the repair is complete

Lets get started.

Tools Checklist

“A mechanic with no tools is like a fish with no water”.

So, here’s a list of tools that you will need to replace a head gasket.

Basic Tools

  • Basic Screwdriver set
  • Rubber Mallet (to free up the cylinder block when removing)
  • Basic ratchet and socket set (socket sizes ranging 8mm to 21mm)
  • A long Pry Bar
  • Car Jack
  • Axle Stands
  • Liquid Paint Marker (for marking timing chain)
  • Engine Degreaser (and a rag)
  • Acetone (small bottle of nail varnish)

Special tools

Here’s a list of specialised tools which are not those that you’ll find a regular toolbox

Tools that You “might” need

Non-essential (Highly Helpful) tools

While it’s certainly possible to complete this repair without the following tools, I’d still highly suggest to have them.

An impact wrench will make easy work of seized bolts, and a breaker bar will increase leverage, improve control, and enhance accuracy.


A mechanic in a workshop disassembling an engine, surrounded by tools and parts. The image features text that reads, 'TEARING DOWN THE ENGINE @Pistontribe.' The mechanic is wearing a dark blue uniform and is focused on his work. Shelves filled with tools and equipment can be seen in the background, with sunlight streaming in through a window.

First things first.

Disconnect the battery, then drain the fluids. This consists of draining the coolant, and draining all engine oils.

Once that’s done, its time to tackle the cylinder head, timing cover, and valve cover.

disassembling An Engine – The Simple Way

I try to simplify engineering. So thats exactly how I teach it.

To date, all the engines I have come across have been built on the same fundamental foundations.

On the bottom end, is the engine block (containing the crankshaft and pistons). On the top end, is the cylinder head (containing the camshafts and valves).

In the middle, is a head gasket, which is sandwiched between the two, to provide an air tight seal. While a timing chain, joins the top and bottom components.

To breath in (i.e., get air), the engine has a air intake system (usually mounted to the front). And, to breath out, there is an exhaust system (usually mounted to the rear).

A turbocharger or supercharger is in other words, an “enhancer”. That works by “enhancing” the already existing applications taking place in the engine.

And while some engines feature two cylinder heads. They are almost always built on the same foundations.

Now you understand engines. The simple way.

It’s time to begin disassembling…

Remove The Valve Cover

As the valve cover is the first point of call, that’s exactly where we’ll start.

  1. Remove the engine cover
  2. Remove all components in air intake system (i.e., air filter, and air intake ducts)
  3. Remove coolant hoses and any hose connected to valve cover
  4. Unclip wiring looms connected to the cylinder head, injectors, and surrounding area
  5. Remove fuel rail, fuel injectors (and high pressure fuel pump if you have one)
    • Remove supercharger (if you have one)
  6. Remove the valve cover

Remove the Timing Cover

In almost all instances, the timing cover must be removed to access the cylinder head.

That being said, the steps to follow for most vehicles consists of:

  1. Jack up the front end of the car
  2. Place axle stands beneath the vehicle
  3. Remove both front wheels
  4. Remove the crankshaft pulley bolt (then remove pulley)
  5. Remove any other component preventing access to timing covers bolts
  6. Remove the timing cover bolts (then remove timing cover)

Some turbo or supercharged cars will unfortunately contain additional steps here.

Subject to the engines design, you may need to additionally:

  1. Remove the front chassis (which can be around 30 mins alone as a DIY project)
  2. Remove the downpipe (i.e., the DPF on diesel cars)
  3. Remove the turbo

Once this is done. Its time to move onto the cylinder head.

Accessing The Cylinder Head Bolts

You should now be able to see the engines camshafts, timing chain, rocker arms and cylinder head bolts.

The next steps are to:

  1. Wrap a flathead screwdriver in a small rag then use it to push back on one of the timing chain guide
  2. Lock the timing chain tensioner in position with a locking pin (or any metal pin you can find)
  3. Use a liquid marker pen to mark three points where the timing chain meets the camshaft gear.
  4. Lock the camshafts if necessary for the engine type
  5. Mark three points where the timing chain meets the crankshaft gear (this will help you to understand where it needs to go back)
  6. Remove the timing chain
  7. Remove the camshaft journal bolts (then remove the camshafts)
  8. Remove the rocker arms making sure they are placed in exactly the same places along side the associated journals. Then store in a place where they will not be moved
  9. Remove the timing chain guides (if necessary)
  10. Loosen each hold bolt about 90° starting from the outside bolts near to the extreme edges and then working your way in to the centre.
  11. Fully loosen all of the cylinder head bolts by following the same sequence

Once bolts in the cylinder head have been removed, its then time to:

  1. Lift the cylinder head up and away from the engine block.

Note that this may take a little wiggling around. So its best to best to keep a rubber mallet handy to help you free the head from engine block.


This image is of a mechanic wearing a blue jumpsuit washing engine parts at a large industrial sink (in a workshop). Various tools are scattered on a nearby workbench, and additional engine parts are laid out for cleaning. The workshop has metal shelving and car parts in the background, illuminated by fluorescent lights, creating an industrial atmosphere

Cleaning the engine (And Associated Parts)

Tools you’ll need:

  • Engine degreaser (or brake cleaner)
  • Acetone (i.e., nail varnish remover)
  • Thread Chasing Kit
  • Engine oil (the required oil for the engine)
  • Plastic or brass scraper
  • Compressed Air (if possible)

Hands down, the best engine degreaser I’ve used to date is STP’s Engine Degreaser. But theres one major gripe that I have with it..

There is simply never enough of it!

The large can comes at 500ml, which is extremely effective on small areas. However, to cover larger areas, such as the entire engine, it’s most cost effective to opt for their multipack option.

Additionally, you can also pressure wash non delicate components (on a low setting). Then use a bristle brush and hand scraper (or ultrasonic cleaner) to clean up the remaining parts.

A good backup to keep is a 5L bottle of Gunk, as it’s an extremely effective product that works well on a variety of vehicles. And while it’s not as penetrative as the STP solution; it will certainly in every case, last for a much longer time.

This image is of a mechanic using compressed air to clean engine bolt holes on a cylinder block, with a cloth to catch debris. Text overlay reads 'CLEANING BOLT HOLES @PistonTribe'.

Clean the Cylinder bolt holes (In The engine block)

Use compressed air (if possible) to blow out loose dirt and debris from the head bolt holes. Alternatively, wrapping a clean rag around a flathead screwdriver, then feeding it down into the hole will also work just fine.

Just make sure to be careful when using the latter method to avoid scratching or damaging the bolt holes. And, additionally ensure that no fluff from the rag is left behind.

The last step is to run a thread chaser through each bolt hold by hand to remove leftover debris. Then you can give each hole a final blast with compressed air.

Please Note: If the thread chaser is difficult to turn (by hand), then the bolt hole is not clean. Conversely, if the thread chaser easily turns, then the bolt hole is sufficiently clean.

This is a close-up image of a mechanic's gloved hand using a scouring pad to clean out a cylinder bore, with text overlay 'CLEANING CYLINDER BORES @PistonTribe'

Clean the Cylinder Bores

The goal with cleaning the cylinder walls is to use non abrasive equipment. And, if you’re using compressed air, then ensure the dirt blows up, and out, of the cylinders.

Finally, using a clean rag, apply a dab of engine oil, then wipe out each of the bores. Additionally wipe down the exposed parts of each piston.

Please Note: If you’re new to the game of mechanics, then avoid using power tools. As it’s easy to cause unnecessary damage in the process.

Clean the engine block Deck And Cylinder head surface areas

A simple razor blade and a little heat will works perfect in removing leftover gasket material. But if that’s not an option, then using a little brake cleaner and a plastic scraper will do just just fine.

Once everything is clean, use a clean dry rag to wipe down both surface areas. Then finally apply a dab of acetone, and wipe down once more for the final time.

Please Note: Surface areas must be left ‘oil free’, unless otherwise instructed by the vehicles manufacturer


This is an image of a mechanic (wearing a grey jumpsuit) inspecting an engine with a flashlight in a dimly lit garage. The mechanic leans in close to the engine bay, using the torch to highlight the parts of the partially disassembled engine. Various tools and parts are scattered around the engine, and metal shelving with car parts and equipment is visible in the background.

Inspecting the engine

What should you be looking for while inspecting the engine?

The general consensus for inspecting a disassembled engine includes, looking for:

  • Signs of physical damage
  • Unusual engine wear
  • Oil or water contamination
  • Visible leaks
  • Damaged or worn electrical connections
  • and improper prior repairs.

It’s unlikely that you’ll return to this area in the near future. So its important to take full advantage of having the opportunity to inspect the engine at such detail.

The following sections will dive into specific inspections for individual areas of the engine. With each test containing a detailed set of instructions for each step that must be carried out. 

Inspecting The Cylinder Head For Warpage

The cylinder head should always be the first point of call (when inspecting an engine for warpage). Being made from aluminium, cylinder heads are more prone to warpage, in comparison to their counterpart, cast iron engine block. 

Aside from this, if an engine block were to distort to the point of warping, it would likely include additional symptoms such as, signs of:

  • Visible cracks or leaks
  • Burning oil
  • Damaged cylinder walls
  • Engine blow-by
  • Or in worst case scenarios, complete failure.

Additionally, because engine blocks are generally cast iron, they retain a higher tolerance to heat, making them less prone to warping when exposed to high temperatures.

That being said, if the car was manufactured in the last ten years, then there’s a high chance that both the cylinder head, and the engine block, are made from aluminium.

Resulting in the entire engine having a lower tolerance to heat than its predecessor.

However, in the event that you discover an engine is warped. Then there is still the option to resurface (i.e. skim) the engine, provided the warpage has not exceeded the manufacturers maximum tolerances.

A great place to find this information is in a Haynes service repair manual, where you find the specific tolerances for the particular vehicle you’re working on. 

Inspecting The Engine Block For Warpage

The key difference in testing the engine block vs testing the cylinder head, is down to the fact that the engine block contains cylindrical bores.

As the bores is where combustion takes place. Temperatures can reach as high as 2,500°F (1,370°C) making the area more prone to warpage, than, anywhere else on the engine. 

Additionally, as the majority of head gasket replacements are carried out with the engine still in the engine bay. It’s very important to choose a straight edge that is both; long enough to measure the engine, and short enough, to fit in the engine bay.

How to Accurately Carry Out An ‘Engine Warpage test’

Required Tools:
  • Feeler Gauge
  • Mechanics machined straight edge
  • Notepad (or notes app on mobile)

Please Note: Testing must be through and exact. Simply put. At this stage, there is no room for error.

Familiarise yourself with using the tools by placing the straight edge on the flat engine surface, and testing varying sizes of the feeler gauge in the gap.

The image below provides a visual example of how to use a straight edge and feeler gauge for testing.


This image depicts a cylinder head warpage check using a straightedge and a feeler gauge. The straightedge is placed across the cylinder head surface in different positions to check for flatness. The diagram in the top right corner illustrates the various measurement positions, marked as A to G, including diagonal, lengthwise, and crosswise orientations. These positions ensure comprehensive coverage of the cylinder head surface to detect any warping or unevenness that would require resurfacing. The technician is shown holding the straightedge in place, demonstrating the correct technique for performing the check.

Checks must be carried out and recorded by following a specific ‘engine warpage check pattern’.

Select the feeler gauge size that corresponds with the manufacturers maximum tolerance for engine warpage. Then begin testing by following the check pattern set below.

The following pattern consists of vertical, horizontal and diagonal checks that should be made when testing for warpage on a 4 cylinder engine.

However, if you are testing an engine that has five or more cylinders. Then the same check pattern should be replicated for the number additional cylinders that the engine contains.

The image is a technical diagram of a cylinder head gasket or a similar automotive component. It shows a top view with four circular shapes that likely represent cylinder bores. The diagram includes labeled points A, B, C, D, E, F, and G, which are connected by straight lines, forming a grid-like pattern. These lines and points are probably used for checking the warpage or flatness of the gasket.
How To assess The test results

The following sections below will help you to determine the actions to take based on your test results. 

A failure is when the feeler gauge passes under the machined straight edge. The result is that the engine has warped by at least the size of the selected feeler gauge.

On the other hand, if the feeler gauge cannot pass under the straight edge, then the test is a pass. And the result is that the engine has NOT warped to the extent of the size selected on the feeler gauge.

Actions To Take – Based On Test Results.

Depending on your results, will determine what actions to take. 

Test ResultAction(s) To Take
Engine is not warped in any way Do nothing
Engine is warped, but has not exceeded the maximum toleranceTake engine to a professional machine shop for resurfacing
Engine is warped to an extent that is beyond the maximum toleranceReplace entire engine (or at least the part of engine which has warped)

typical Maximum ‘warpage Tolerances’

The next section will provide examples of tolerances in engine warpage you can typically expect to find for a few of the most current popular selling cars.

Disclaimer: The values in the following tables are “general guidelines”. Engine specifications and tolerances can vary significantly across manufacturers. Always refer to the vehicles service manual for the most accurate information.

Below are the typical tolerances for varying engine types categorised by number of cylinders.

Engine ConfigurationMaterialMax Warpage (inches / mm)Action
Inline 3 (I3)Aluminum0.003 in / 0.076 mmResurface/Replace
Flat 4 (Boxer 4)Aluminum0.003 in / 0.076 mmResurface/Replace
Inline 4 (I4)Aluminum0.003 in / 0.076 mmResurface/Replace
Inline 6 (I6)Aluminum0.004 in / 0.102 mmResurface/Replace
Flat 6 (Boxer 6)Aluminum0.004 in / 0.102 mmResurface/Replace
V6Aluminum0.004 in / 0.102 mmResurface/Replace
V8Aluminum0.004 in / 0.102 mmResurface/Replace
V10Aluminum0.005 in / 0.127 mmResurface/Replace
V12Aluminum0.005 in / 0.127 mmResurface/Replace

Here’s a chart summarising the cylinder head warpage tolerances for 10 popular vehicle makes and models in the UK:

ManufacturerModel (Engine Model)MaterialMax Warpage (inches / mm)Action
FordPuma (1.0L EcoBoost I3)Aluminum0.004 in / 0.102 mmResurface/Replace
KiaSportage (1.6L T-GDi I4)Aluminum0.003 in / 0.076 mmResurface/Replace
NissanQashqai (1.3L DIG-T I4)Aluminum0.004 in / 0.102 mmResurface/Replace
VolkswagenGolf (1.5L TSI I4)Aluminum0.004 in / 0.102 mmResurface/Replace
VauxhallCorsa (1.2L Turbo I3)Aluminum0.003 in / 0.076 mmResurface/Replace
HyundaiTucson (1.6L T-GDi I4)Aluminum0.003 in / 0.076 mmResurface/Replace
BMW1 Series (1.5L Turbo I3)Aluminum0.003 in / 0.076 mmResurface/Replace
MGHS (1.5L Turbo I4)Aluminum0.003 in / 0.076 mmResurface/Replace
AudiA3 (1.5L TFSI I4)Aluminum0.004 in / 0.102 mmResurface/Replace
VolkswagenT-Roc (1.5L TSI I4)Aluminum0.004 in / 0.102 mmResurface/Replace
Information collected from Rac.co.uk – most popular cars sold in UK 2024

Heres a list with the top selling US vehicles in 2023 and their associated warpage tolerances:

ManufacturerModel (Engine Model)MaterialMax Warpage (inches/mm)Action
FordF-150 (3.5L EcoBoost V6)Aluminum0.003 in / 0.076 mmResurface/Replace
ChevroletSilverado 1500 (5.3L V8)Aluminum0.004 in / 0.102 mmResurface/Replace
Ram1500 (5.7L HEMI V8)Aluminum0.004 in / 0.102 mmResurface/Replace
ToyotaRAV4 (2.5L I4)Aluminum0.002 in / 0.051 mmResurface/Replace
HondaCR-V (1.5L Turbo I4)Aluminum0.003 in / 0.076 mmResurface/Replace
NissanRogue (2.5L I4)Aluminum0.002 in / 0.051 mmResurface/Replace
JeepGrand Cherokee (3.6L V6)Aluminum0.003 in / 0.076 mmResurface/Replace
GMCSierra 1500 (5.3L V8)Aluminum0.004 in / 0.102 mmResurface/Replace
ToyotaCorolla (1.8L I4)Aluminum0.0028 in / 0.071 mmResurface/Replace
ToyotaCamry (2.5L I4)Aluminum0.003 in / 0.076 mmResurface/Replace
Information referenced from the top selling US cars in 2023.

What Is resurfacing (i.e., skimming An engine)?

Engine resurfacing, commonly known as “skimming the engine,” is a machining process where a thin layer of material is removed from the surface area of the cylinder head, engine block, or both.

A metal cylinder head being resurfaced on a milling machine. The machine's circular cutting tool is smoothing the surface of the cylinder head to restore its flatness, ensuring a proper seal when reassembled with the engine block.

The purpose of this procedure is to restore a perfectly flat surface, and provide a proper seal between the head and the block with a head gasket installed.

Proper sealing is crucial for maintaining engine compression, preventing coolant or oil leaks, and ensuring overall engine performance.

How much Can Be removed When Resurfacing?

The amount of material that can be removed when resurfacing is directly determined by the distance that the piston must travel, to reach top dead centre (i.e., TDC).

Additionally, this process must ensure that the amount of removed material does not compromise the clearance between the piston head and valves. As reducing the clearance could result in the piston and valves crashing with one another.

The examples below contain the maximum resurfacing tolerances you can typically find for the most popular selling engines.

Make & ModelEngineMax Skim (Cylinder Head)Max Skim (Engine Block)Side Notes
Ford Puma1.0L EcoBoost0.2mm / 0.0079 inches0.1mm / 0.0039 inchesEcoBoost engines are highly sensitive to compression changes, so skimming should be minimised.
Kia Sportage1.6L T-GDi0.3mm / 0.0118 inches0.15mm / 0.0059 inchesHigher tolerance due to turbocharging. Check the gasket type before skimming.
Nissan Qashqai1.3L DIG-T0.2mm / 0.0079 inches0.1mm / 0.0039 inchesSmall allowances due to the compact engine design.
Volkswagen Golf1.5L TSI EVO0.2mm / 0.0079 inches0.1mm / 0.0039 inchesEnsure even skimming to maintain combustion chamber shape.
Nissan Juke1.0L DIG-T0.25mm / 0.0098 inches0.15mm / 0.0059 inchesSimilar to Qashqai, care must be taken with turbo models.
Audi A32.0L TFSI0.25mm / 0.0098 inches0.12mm / 0.0047 inchesPerformance-oriented, so tolerances are tighter.
MG HS1.5L Turbo0.3mm / 0.0118 inches0.15mm / 0.0059 inchesRelatively high tolerance for a small displacement turbo engine.
Hyundai Tucson1.6L T-GDi0.3mm / 0.0118 inches0.15mm / 0.0059 inchesSimilar to Kia Sportage, these engines can tolerate more skimming.
Peugeot 2081.2L PureTech0.2mm / 0.0079 inches0.1mm / 0.0039 inchesEngine’s compact design requires careful skimming.
Vauxhall Corsa1.2L Turbo0.2mm / 0.0079 inches0.1mm / 0.0039 inchesLimited skimming allowances due to small engine size.

Inspecting The Remaining Engine components

The following checklist contains inspections that should be carried out, after the checks on the cylinder head and engine block have been completed.

Carefully follow each of the instructions and take notes where necessary. 

Inspect the gasket for signs of wear, cracks, breakage, oil buildup, dark spots, rust, and any deformation or warping that could affect its seal. Note abnormalities, then continue inspecting the remaining components. Check out our examples to visually see how a failed head gasket looks.

Place the cylinder head on a flat surface. Pour a small amount of liquid (like kerosene or fuel) into the intake or exhaust ports. Check if any liquid seeps through the valve seats; if it does, the valves are leaking and need further inspection or replacement.

Inspect the pistons head carbon buildup, cracks, or pitting. On the top of each piston is a spray pattern left from the burnt fuel of the fuel injectors, which is great for comparing inconsistencies across pistons.

Check the camshaft lobes for signs of wear, scoring, or pitting. Rotate the camshaft and visually inspect each lobe for damage. Lobes should be smooth with no rough spots, no indentations or excessive wear.

Inspect the camshaft journals for scoring or wear marks. Use a micrometer to measure the journal diameter, comparing it to the manufacturer’s specifications. Check bearings for wear, cracks, or scoring.

Check each rocker arm for signs of wear, damage, or excessive play. Roll them on a flat surface to identify stiffness. Inspect the rocker arm shafts and bushings for wear or pitting. Replace any damaged components.

Visually inspect the valve springs for cracks or signs of wear, and replace any weak or damaged springs.

Insert the valve stem into its seat (i.e., the valve guide), and feel for excessive play. Too much movement indicates wear in the guide, requiring replacement or reaming with oversized valves.

Inspect the part of the cylinder bore that you can see for any signs of excessive wear, damage or cross contamination.

Inspect all oil passages for blockages or debris. Use compressed air to blow out any obstructions and ensure free-flowing passages.

Inspect the timing chain or belt for wear, cracks, or stretching. Check the tensioner for smooth operation and proper tension. Replace the chain/belt and tensioner if any issues are found.

Check all gasket surfaces for scratches, nicks, or warping. Use a straightedge to ensure surfaces are flat. But ensure to clean first.

Inspect freeze plugs for damage, rust, leaks and corrosion: Freeze plugs, also known as core plugs, expansion plugs, or frost plugs, are small, circular metal plugs in the engine block. They are highly prone to corrosion and usually located down the sides and rear of the engine block.

With the cylinder head and engine block now resurfaced, or within spec. And the remaining components all checked, repaired and replaced.

Its now time to begin reassembling engine.


This image is of a mechanic assembling an engine under the hood, using a power tool, with text overlay 'ENGINE ASSEMBLY @PistonTribe'.

assembling the Engine

Reaching this point is a great milestone, but still way too soon to take your foot of the gas.

Assembling the engine is essentially doing what you did on removal, in reverse. A simple way to keep track is to use a checklist.

Lets begin with the gasket.

Installing A New Head Gasket

Please note: Some head gasket installations require the addition of liquid seal, while others don’t. So it’s important to check the vehicles service manual for the most accurate information.

Which Side Of the gasket Should Face Up?

Some products have clear instructions, while other don’t. And, unfortunately, in the motor industry; this has seemed to become the norm.

That being said, if the gasket you’re installing has no instructions, then you can also look out for:

  • A Branded Label or symbol: Even a manufacturers label on the product will be on the side that must face up
  • Colour coding: blue side facing up and black side facing down
  • A difference of Texture or pattern: Striped side up and plain or flat side must face down

And if all the above fails, then there’s one last indicator that you might come across.

The answer…. FIRE RINGS!

Not as easy to identify for the newbie DIY engineer, but the difference in design of the fire rings can be a clear indication of the correct way to install the gasket.

The images below provide two examples identifying the differences in design of the fire rings on each face.

image of fire rings clearly joining with one another

Fire rings join with one another. This side must face down and mate the deck of the engine block.

Image showing the fire rings of the head gasket not touching

Fire rings are separated. This side must face up and mate the surface of the cylinder head.

If All Else Fails!

Then, there is one last way. But to tell you, I would have to…

Jokes aside, in the case the head gasket has;

  • No instructions
  • No label or distinct colouring
  • No branding
  • No differences in texture
  • And no differences in design on the fire rings

Then there is one final way, and that way is; there is no other way.

Let me explain.

Most engine blocks contain dowel pins which are uniquely positioned to prevent incorrect instalment of the cylinder head, and head gasket.  

In fact, in many cars like my own, the gasket is designed in such a way that it can only fit on the engine block on one specific side, and in one specific orientation. As installing the gasket any other way would result in misalignment of the holes of the gasket, and the passageways in the engine block.  

This explains why some gaskets come with no instructions. As being truthful, in some cases; they’re simply not needed. 

 A few general guidelines to follow when fitting a new head gasket is to: 

  1. Ensure the surface area of the engine block is clean
  2. Locate the dowel pins on the engine block and cross reference each position with the holes of the gasket
  3. Test fit the head gasket to ensure all the holes correctly align with the corresponding passages in the engine block (check to that the gasket is also on the correct facing side)
  4. Fit the head gasket for the final time (in accordance with the manufacturers guidelines)


Installing The Cylinder Head

With the gasket installed, it’s now time to install the cylinder head.

Tools you’ll need: 

  • Rubber gloves (to lift the cylinder head) 
  • Assembly lube
  • Engine oil
  • Torque wrench (for head bolts and bolts in the camshaft journal caps) 
    • Additionally Use a torque angle Gauge to improve accuracy when tightening bolts
  • Liquid marker pen (mechanics pen to mark head bolts)

Install the cylinder head by carrying out the the following steps: 

  1. Put on a pair of protective gloves. As most cylinder heads contain many sharp edges 
  2. Check the location of the dowel pins on the engine block, then Lift the head cylinder onto the head gasket
  3. Lightly dab some oil onto each cylinder head bolt. This is to reduce the chance of false torque readings as a result of dry threads 
  4. Drop the cylinder head bolts into each of the head bolt holes, then hand tighten each of them. There is no specific order to follow at this time
  5. Check the service manual for the correct tightening sequence to follow 
  6. Use a torque wrench (and the shortest viable extension bar) to tighten each bolt to the correct torque, while following the recommended sequence (usually starting in the centre and moving outwards) set by the manufacturer. 
  7. Use the liquid pen to mark from 12 o’clock to 6 o’clock Then use this as a reference of where to make turns of particular degrees. Or you can use a torque angle gauge for the most accurate results. 
  8. Install the hydraulic valve lifters (or pushrods) depending on the engine type
  9. Install the rocker arms making sure to place them back in the correct way, and in the exact locations they came from
  10. Install the intake and exhaust camshafts to their respective positions and tighten each of the journal caps in the exact sequence set in the vehicles service manual
    • Additionally install the camshaft gears if necessary 
  11. Apply assembly lube in all areas where metal on metal contact is present. This includes the top of valve springs, camshafts, pushrods (if you have them), and hydraulic lifters. 
  12. Pour fresh engine oil over the cylinder heads of the entire internal assembly. This will ensure that all components are well lubricated on the initial startup.


 "Diagram of an engine's timing chain system, showing key components labeled. At the top is the camshaft sprocket, with a timing mark and plated link indicated. The timing chain runs around this sprocket and down to the crankshaft sprocket at the bottom. The chain is guided by right and left chain guides, with a tensioner sleeve and a rubber sheet also labeled near the crankshaft sprocket. The diagram also marks the timing marks (punches on sprockets) and sprocket holder.

Please Note: If the car you’re repairing is chain driven, then you’ll need to install the timing chain and timing cover before you can install the valve cover.

However, if the engine features a timing belt (instead of a timing chain), then you’ll need to install the valve cover, timing cover (if there is one), pulleys, gears, and oil pan, in prior to installing the belt.

Installing A New Timing Chain Or Belt Kit 

If you’ve been following this far, and also planned to reuse the existing timing chain (or belt). Then you should have marked and fastened the chain (or belt) as instructed when disassembling.

However, if the car has covered more than 30k miles since the last timing chain (or belt) replacement. Then now is the perfect time to do so.

Tools you’ll need 

  • A Torque wrench
  • A set of Socket and wrenches
  • Flathead screwdriver 
  • Liquid pen (mechanics pen) 
  • Engine assembly lube
  • Engine-specific: Camshaft locking tool 

The following section contains a list of general guidelines that should be followed when installing a new timing chain on a majority of vehicles. 

  1. Set the piston of cylinder number one to top dead centre. This can be done by inserting a long screwdriver to the injector hole of cylinder number one. Then to find TDC, rotate the crankshaft pulley clockwise until the screwdriver reaches its highest possible point, before coming back down. 
  2. Align the camshaft timing marks with one another (including the marks on the engine block if required)
  3. Lay the timing chain or belt over the camshafts and crankshaft gear. Ensuring that the coloured links or timing marks on the belt line up with the associated marks on the gears
  4. Install the timing chain/belt tensioner (or reset the old one if you’re reusing it)
  5. Re check all timing marks are aligned to their correct positions
  6. ‘Manually’ turn the engine for two full revolutions, then check the timing marks on the camshaft’s line backup as theyYou  did at the start. If the timing marks do not realign, then remove the chain or belt, and restart from step number 3.
  7. Rotate the engine at least 6 more times to ensure the timing is correct. 
  8. Re install the timing cover and continue the reassembly

Re install the remaining components

While the finish line is near, we are not quite there, just yet. Instead, what’s most important at this stage, is to remain focused. As it’s far easier to make mistakes when you think you’re in the clear.

The long and short is. Don’t get complacent.

First things first. Install the valve cover, and tighten each bolt to the recommended torque. Next, install the turbo, install the coolant pipes, install the oil feed pipes, and install the intake and exhaust manifolds.

Next, install the fuel lines, injectors, downpipe and wiring loom. Then, install the air intake system, alternator (if required), and any remaining components that were removed but has not been mentioned.

But do not install the spark plugs (or glow plugs) as we will need these out to run a compression test before starting the engine.

Lastly, reconnect the battery it was disconnected.

Testing and Final Checks

Once the components are back in position, its time to focus on fluids.

Refill All fluids

Top up the coolant in the coolant reservoir, and refill the engine oil to the required level specified on the oil level dipstick gauge.

Prime the oil system

  1. Ensure the spark (or glow plugs) are removed from the engine.
  2. Turn on the ignition without starting the car. Leave on for around 6 seconds, then switch off ignition.
  3. Locate and remove the fuse for the fuel pump (safest option). Or if you cant find it then disconnect the wiring to the fuel injectors (not as safe as may cause flooding of cylinders)
  4. Crank the engine for 10 – 15 seconds making sure to rest the engine for at least 2 minutes between cranking.
  5. Repeat the previous step (i.e., cranking) 3 more times, then re attach all components (except the wiring to the fuel injectors if already disconnected).
This is an image of the engine bay in a Mazda CX-5 diesel engine with the high-pressure fuel lines highlighted. Red arrows point to the fuel line connectors attached to the fuel injectors, while yellow boxes outline the critical connection points of the fuel rail to the injectors. The engine has several visible components, such as the fuel injectors, fuel rail, hoses, and electrical connectors. The image focuses on the key fuel system connections, which is associated to the section in this article about bleeding the fuel system.

Bleed the Fuel System (diesel Cars Only)

As most petrol engines are self priming, you will only be required to complete this step on a diesel. 

The short explanation is: If working on a diesel engine then always bleed the fuel system. 

Please note: You should NEVER skip this step on a diesel engine as doing so will 100% catch you out if the engine does not start after the rebuild. Don’t skip it.

The long explanation is: Modern diesels that feature a common rail system will typically inject fuel at 15,000 to 30,000 psi (around 1,000 to 2,000 bar), while a petrol fuel system will inject at just 500 to 3,000 psi (about 35 to 200 bar).  

With diesel fuel having a higher flash point (typically 52-96°C (126-205°F) over petrol at just -43°C (-45°F), diesel is inherently more difficult to ignite, and in turn, more susceptible to air contamination.  

The higher flash point of diesel means it is unable to vaporise as readily as petrol. Resulting in the need for diesel to be injected at higher pressure in order to create the mist (of atomised fuel) that is required for effective combustion. 

This procedure will require a second person, so grab a friend for some assistance:  

how to Bleed a diesel engines fuel system

Note that some diesel engines will have a bleed nipple, but Iv’e found this method to be often ineffective

  1. Slightly slacken the nut (just one) of the first high pressure fuel line that mounts to the fuel injector (as highlighted in the image above) 
  2. Crank the engine for 10 – 15 seconds until you see bubbles. Then continue cranking until you see a steady stream of diesel running with no bubbles 
  3. Tighten the nut once you are confident there are no more bubbles (i.e. contaminating air) in the system
  4. Repeat the previous steps for the remaining fuel injectors (i.e. cylinders) on the engine 

Once this is done, move onto the test below.  

Perform an engine compression test

Please note: You will need a second person to perform this test

Note the satisfactory minimum and standard compression readings shown in the vehicles service manual. Additionally note the maximum allowable pressure difference between cylinders in the service manual. 

  1. Remove all spark plugs (or glow plugs) from the engine. 
  2. Unclip wiring to the fuel injectors (or remove fuel pump fuse) 
  3. Insert (screw in) the long tube of the compression tester to the spark plug (or glow plug hole) of cylinder one
  4. Crank the engine for 10 – 15 seconds 
  5. Note the reading and leave for 2 minutes and recheck reading to ensure that pressure additionally held at initial level 
  6. Release the pressure in the compression tester (via the pressure release valve) 
  7. Rest engine for around 2 minutes
  8. Repeat this process for remaining cylinders on the engine (making sure to take detailed notes) 

Assessing the results.

  • If the readings of any cylinders were lower than the satisfactory minimum compression level specified in the vehicles service manual, then there is a fault in the specific cylinder that must be further investigated
  • If the readings across each cylinder is by a larger margin that what is allowable by the manufacturer, then there is a fault in one or more cylinders that must be further investigated 
  • If compression readings are within the satisfactory limits set by the manufacturer, then the test is a pass and the repair is complete. 
  • If the difference of readings across cylinders does not exceed the maximum allowable tolerance set by the manufacturer, then the test is a pass and the repair is complete.

Visually Inspect The Engine 

The purpose of a visual inspection is to identify abnormalities before starting the engine. This could be a leak, crack, loose nut or bolt, damaged wire or missing part. 

Inspect, inspect, inspect. You can never check too much, as now is the time where you want to fix problems as opposed to when the engine is running and under stress. 

Once you are happy with the checks, it’s time to move onto the final stage. 

Fire Up The Engine 

Reconnect the remaining components which have been removed. I.e., glow plugs (or spark plugs), and fuel injectors.

Remember: The engine requires three elements to successfully start and run 

  1. Air 
  2. Fuel 
  3. Ignition 

Ensure that all fuel lines are good and injectors are good. Ensure air filter, intake manifold and turbo (if you have one) is good. 

Then ensure connectors and bolts for fuel injectors are good. 

Next, crank the engine for 10 – 15 seconds.

Continue checking while cranking for

  • Unusual sounds 
  • Leaks 
  • Unusual Smells 
  • Excessive smoke in a particular area – although a little smoke is 100% expected on first start up 

If the car starts, then woohooooo! Well done. But we are not finished yet.

On the other hand, if the engine doesn’t start, then do not worry. However, you will need to go back and investigate the following areas: 

  1. Air system 
  2. Fuel system 
  3. Ignition system 

Stationary Vehicle Assessment: How Does The Engine Run?

With the engine running, it’s now time to assess the following:

  • Does the engine misfire run smoothly?
  • Is there excessive smoke coming from any area of the car?
  • Is the coolant bubbling in the reservoir?
  • Does the in car heating work?
  • Are all lights working?
  • Are the fans kicking in at the correct time to cool down the engine?

If any of the above is a fail, then switch off the engine and investigate.

If everything is good, then it’s time to take the car for a test drive.

Driving The Car For the first Time

The first drive of the car should be focused on assessing the engine’s performance, unusual lights on the dashboard and unusual smells.

Drive the car for around 15 minutes making sure to use a variety of roads that include hill climbs, downhill gradients and a series of turns.

While driving you should make the following checks:

  • Is the temperature gauge building up or remaining at normal?
  • Can you hear unusual sounds such as engine knocking, grinding or whining?
  • Is there excessive exhaust smoke?
  • Are there any warning lights on the dashboard?
  • Are there unusual smells coming inside the cabin?

Once you return back. Re perform the stationary vehicle assessment.


5 Mistakes To Avoid When replacing A head gasket

I’ve seen and made a whole bunch of mistakes in the past. But the following five in this list are among the most common, and most costly, I have personally witnessed. 

Innocently trying to save time, or save money can become real expensive. So here’s a few ways to avoid it.

Mistake #1 – The Worst And most common

Reusing old cylinder Head stretch bolts

I’ve come across YouTube videos with others making this mistake. Let me be clear. AVOID doing this, at all costs. 

Cylinder head bolts are designed to stretch. Meaning, when you tighten them down, they elongate. Resulting in them having a one-time-usage.

For one, there is already a confirmed failure in this area. So why take the risk of having to make this entire repair again?

By far this is the most common mistake, and can result in a cracked engine block, continued failure or non starting engine. Avoid.

Mistake #2

improper Engine cleaning (When Disassembling)

The short and sweet is, don’t rush this repair.

Failing to thoroughly clean the engine block deck and cylinder head surface areas is a fast track to failure. 

Both surfaces must mate with a flush fit to create an effective seal. Dirt or debris in this area can result in improper sealing, and low engine compression. 

Furthermore, tightening down an offensive object between two flat surfaces can result in cracks, leaks and false readings on torque wrenches. 

So always ensure to thoroughly clean surfaces and bolt holes as objects or particles in these areas are notorious for resulting in unnecessary issues.

Mistake #3

Not taking the cylinder head to a machine shop

This mistake is an odd one. It never really matters till the engine is pieced back together, and a new problem presents itself. 

That’s when it becomes vital. As you begin to question if there was a crack, leak or uneven surface that you missed hen making the repair. 

And for what is usually a cost of less than £100, it is well worth taking the engine to a professional machine shop. This way you can be confident that you are rebuilding an engine with no further faults. 

A DIY toolkit has its limitations. Point blank period. So let the professionals do what they do best. 

I have personally made this mistake in the past. Only to find out that I had to start out all over again after already rebuilding the engine.  

AVOID!

Mistake #4

Misdiagnosing the issue (i.e., Making Assumptions)

Ever realised that everyone becomes an expert whenever your car develops an issue. I have. 

But simply following the information of others without a clear diagnosis can lead you straight down a path to disappointment. 

Instead, always carry out a proper fault diagnosis and correctly identify the faults before starting the repair.

Mistake #5

Using poor quality (or incorrectly installing) parts

Ever heard the saying “You get what you pay for”. 

There’s some truth to this.

As cheaping out on parts is a fastrack to failure. Vital engine components should not be messed with.

And besides, if you’re already saving on labour cost, then why not go all in on quality. 

The second part of this mistake is made by not following manufacturers guidelines in installation. Long story short, if it’s not in the book, then don’t do it.

This means, no liquid gasket, no washers and no missing or skipping torque settings. AVOID! 

I have made this mistake many times and paid the cost. Don’t do it!


Questions To Ask (Before Carrying Out This Repair)

A head gasket can fail for a number of reasons, but the most common is because of overeating. So the question to ask is, what causes an engine to overheat.

In which the reply is; from a faulty water pump, thermostat, radiator, fan, low coolant levels, or lack of lubrication.

Surprisingly, aside from a torque wrench, and potentially a straight edge, there are not any special tools required to replace a head gasket. Instead, the success of the replacement directly correlates with the access you have to the manufacturers guidelines.

A professional mechanic with all parts to hand can complete this repair in 5 hours. However, a DIY mechanic with no ramp, previous experience, or access to professional equipment will typically take around 8 hours to 3 days to complete this repair. 

The short answer is; it depends. As the only time a sealer would work is if the gasket is partially blown. There are no guarantees. 

And besides, I am yet to find a liquid sealer that repairs a physically damaged metal component. 

So the only time a sealer would make sense is if you needed to get the car home (to make the repair), or to a scrap yard.

A blown head gasket is not always an indication of a damaged engine. But it certainly is an indication of an engine operating incorrectly.

As a gasket is designed to take the hit when the dominoes begin to fall, it is first inline to blow before anywhere else in the engine is damaged. Because of this, it’s totally possible to find a blown head gasket with all other components intact.

A successful head gasket replacement will result in a smooth delivery of power, consistent idle, and normal operating temperatures. Additionally, there should be no leaks, no fluid contaminations, and no reduction in levels of the engine’s compression. 

Failing to promptly replace a blown head gasket will in all cases result in complete engine failure. Oil mixing with coolant, or either fluid escaping from their normal pathways will result in poor lubrication, inadequate cooling, and catastrophic internal engine damage.

The most common type of gasket used in modern cars are MLS (multi-Layer Steel) gaskets usually consisting of 3 – 5 layers. To date, they retain the most durable and cost effective design. 

But it’s also common to find copper gaskets Elastomeric (i.e., silicone) gaskets used in performance cars. And while they are more expensive, they offer far better durability, flexibility, and increased tolerance for a wide range of applications. 

Replacing an engine’s head gasket will always reduce the car’s resale value for honest sellers. The simple reason is; an engine which has never had issues is far more appealing to a wider range of buyers over an engine that is like frankenstein. 

Yes, cross contamination of fluids will always result in an increase of emissions. And the result of increased emissions equals excessive exhaust smoke.

The short answer is never. Or in other words, when it blows. As a head gasket in a well maintained vehicle can last the lifetime of the engine. With the average lifespan for an engine being 150,000 miles, a head gasket should last just as long.


A frustrated man sitting next to a car with the hood open. His hands are grease-stained, and tools are scattered around, indicating an attempt to repair the head gasket. Despite his efforts, the car is still not functioning properly. The man has a defeated expression, and the scene is set in a home garage or driveway, under an overcast sky, adding to the mood of frustration


Unexpected problems That Can occur replacing The Head Gasket

Sometimes things just don’t go as planned. And that’s ok! 

But that doesn’t mean you should give up. As through trial and error is learning. So stick to it, and you’ll figure it out. 

I love to live by “most things are repairable. It’s just that, some things are more expensive to repair than others”.

Regardless, here are some common issues that you may come across after a head gasket replacement; 

  • Coolant or oil leaks
  • Overheating
  • White smoke from the exhaust
  • Loss of power or misfires
  • Coolant contamination in the oil (or vice versa)
  • Improperly torqued head bolts
  • Air pockets in the cooling system
  • Warped or cracked cylinder head or block
  • Improper timing
  • Excessive oil consumption
  • Exhaust gas in the cooling system
  • Check engine light
  • Water pump or thermostat failure
  • Poor fuel economy

Any of the above warrants further investigation. But don’t beat yourself up. As in most cases a simple tweak is all it needs. 

Further issues you might see include: 

  • Engine management light – This can result from disconnecting various mechanical components resulting in the ECU detecting a fault or miss reading when reconnected
  • Malfunctioning electronics (inc keys and alarms) – The battery being disconnected for an extended period of time can result in particular components requiring reprogramming to function correctly again. The good news is that if the engine is running then rest is a piece of cake.

How to prolong the life of a head Gasket

The most effective way to extend the life of a head gasket is to prevent driving a car when the engine is overheating. This means, faulty thermostat, stop, faulty fan, stop, faulty whatever it is, stop, call a recovery and prevent the cause of further damage. 

Aside from this, making sure that coolant is always topped up, and not leaking. Making sure that oil is topped up, and not leaking are the two best ways to maintain the life of a head gasket.

Conclusion

The most hilarious part of this post is the fact that it took longer to write this post than to make the repair.

And while a head gasket failure is a major issue, I hope that this post was able to simplify the concepts, amplify the symptoms, and help you to define a clear path for the repair.

Picture of Leon Angus

Leon Angus

I love bikes. All types, but mainly motorbikes (or motorcycles for those in the U.S.). I also love cars, planes and boats too! I'm a qualified Motorsport Engineer that currently lives in the UK and drives trains for a living (weird combo, don't ask), I love to cook, into fitness and love to smell petrol in my spare time! A true petrol head at heart. This website is my path back into the motor industry and the place where I can shell fuel for fanatics along the way. Learn More about the mission here

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Picture of Leon Angus

Leon Angus

I love bikes. All types, but mainly motorbikes (or motorcycles for those in the U.S.). I also love cars, planes and boats too! I'm a qualified Motorsport Engineer that currently lives in the UK and drives trains for a living (weird combo, don't ask), I love to cook, into fitness and love to smell petrol in my spare time! A true petrol head at heart. This website is my path back into the motor industry and the place where I can shell fuel for fanatics along the way. Learn More about the mission here

About Piston Tribe

Welcome to Piston Tribe, a place where bikers and drivers (just like you) can find tips, recommended gear, tools and techniques for maintaining the health of your bike, car, scooter or whatever floats your boat (pun intended… as we cover boats too). 

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