What is a cylinder head gasket ➤ AUTODOC CLUB

The cylinder head gasket acts as a seal between the engine block and cylinder head. Its primary function is to prevent a loss of compression and to stop engine gases from escaping. It also keeps the cylinders, engine oil and coolant separate from each other, ensuring that the coolant and oil don’t mix. The gaskets play an essential role in maintaining engine power and a blown or damaged head gasket can have serious consequences for the engine.

Modern cylinder gaskets are usually made from multi-layered steel joined together with elastomer. These components are durable and long lasting as they are able to withstand high pressures. However, some vehicles use copper gaskets, such as cars with high performance street engines. Copper distributes heat evenly, preventing warping. In the 70’s and 80’s, composite head gaskets made from graphite and asbestos were very popular, as they were resistant to corrosion. Nowadays, composite components are rarely installed, mainly because they are prone to leaks and have a short service life.

Common causes of head gasket failure

Overheating. When the engine gets too hot it can cause warping and blow the gasket. This could eventually require expensive repairs. Causes of overheating include coolant leaks, broken coolant fans and blocked passages, etc.
Wear. Like most other car parts, they wear over time, leading to leaks and other issues. It is important to replace the gasket on time or as recommended by the manufacturer to avoid costly repairs.
A damaged engine block or head. This may reduce the gasket’s effectiveness as a seal.
Installation errors. E.g. incorrect torque.

Symptoms of a faulty head gasket & how to test it

Do you think there might be a problem with your engine?

Look out for these signs of a blown cylinder head gasket:

Coolant or oil leaks. Worn gasket seals are one of the main causes of oil leaks. When the head blows, oil and coolant will often leak out from between the head and engine block.
Contaminated oil. You may see a milky substance around and under the oil cap. This is caused by the coolant and oil mixing together when there is a leak.
White smoke. Indicates a leak and a loose or damaged gasket.
The radiator needs to be topped up with water or coolant very frequently. This could be due to a leak or regular overheating.
High temperature readings on the engine gauge. This is one of the most common symptoms.
Engine misfire.
Pre-ignition. Often caused by a buildup of carbon deposits and cooling system problems. Carbon buildup can cause an unhealthy increase in compression, putting excessive pressure on the gasket seals.

Testing: Please make sure to wear protective gloves and other safety equipment while conducting these tests.

Remove and inspect the oil filler cap for abnormal substances.
Remove the spark plugs and inspect them for leaks. To test for leaks, pressurise the spark plug holes and crank the engine. If any coolant appears in the holes, there is a leak. You can also test the compression of the cylinders.
Remove the radiator cap and check for bubbles with the engine running. Blown gaskets release gases into the coolant system creating bubbles.
You can check for the presence of gases in the cooling system using a chemical/leak tester. Read through the tester instructions carefully before carrying out the test.

Repair & maintenance tips

Due to the potential complexity and importance of cylinder head gasket repairs, it is generally recommended to pay a mechanic to do this for you. However, if you have the necessary skills and would like to save money, there are a few things you could do yourself. If the damage is minor and the engine can run for at least 15 minutes without overheating, it may be possible to use a head gasket sealer to fix small cracks in the cylinder head, leaks, and holes.

Preventing gasket failure:

Check the cooling system regularly to make sure it is in a good working condition.
Change the coolant regularly, as advised by the vehicle manufacturer.
Some people recommend flushing the engine regularly to prevent and get rid of carbon deposits which build up in the combustion chambers.
Make sure you use the correct tools and torque when installing a new component.

Frequently asked questions

⚠ How often should I replace my cylinder head gasket?

Modern head gaskets are very durable and generally last up to 200,000 miles, lasting as long as the car engine itself. However, it is advisable to conduct regular checks and act quickly when a problem is detected. It is much more cost effective to replace a head gasket than to pay for repairs for engine damage caused by a broken one.

⚠ How long does it take to install a new head gasket?

Replacing the head gasket can be quite a time-consuming task and it depends on the skills and experience of the person installing the part. It can take anything between a few hours and several days in extreme cases.

⚠ Am I still able to drive my car with a blown head gasket?

This is strongly advised against as it could lead to serious damage, requiring a complete engine replacement. The lack of engine stability caused by this poses a risk to the driver and passengers.

Den

a smiley technician with plenty of experience starring in AUTODOC's video tutorials; Never seen without his goggles; races his BMW X5 E53; dreams about receiving a Gold Play Button for getting 1,000,000 subscribers on YouTube.