What Is a Cylinder Head Gasket ?


Nov 25th, 2021

What Is a Cylinder Head Gasket ?

What is a cylinder head gasket, what does it do, and what are the symptoms that it’s going bad? Is it expensive to replace?

These are just some of the questions that running in your mind if you hear the mechanic suggest that you have a blown head gasket. Blown what? – you might hear yourself murmur quizzically. 

Sadly, the cylinder head gasket is one of those car parts that you only become interested in when it starts to fail. Let’s clear your confusion in this post.

The Cylinder Head Gasket

What is it and what does it do?

A cylinder head gasket is a component of a car engine that separates mediums like oil and water in the engine and acts as an external seal. 

It acts as a seal between the cylinder head and engine block and has cylindrical bored holes that hold the pistons. As such, gaskets must be hard-wearing to withstand internal pressures.

What is the head gasket made of?

The cylinder head gasket material used in engines varies – some are interleaved sheets of steel and elastomer, some are solid 'O-ringed" sheets, and some are composites of two or more industrial materials. 

Symptoms & Causes of Blown Head Gasket

You may not notice a burst head gasket straightaway. Fortunately, there are head gasket symptoms that you can look out for.

What are the symptoms of head gasket issues?

The following signs should be enough to give you a heads-up that the gasket might be broken and need to be replaced. 

  • Overheating – this symptom becomes more noticeable the further you drive, probably due to a restricted radiator.
  • Milky leak – this is the result of coolant contaminating the oil; you’ll usually find this milky grime inside the oil filler cap. 
  • White smoke – sweet-smelling white smoke coming out of the exhaust pipe is a sign of a bad head gasket that causes leaking coolant/antifreeze to vaporise and escape out of the tailpipe. 
  • Bubbles in the radiator (or overflow tank) – this usually happens when air goes into the cooling system. 
  • Low-running engine – a bad head gasket causes loss of compression, resulting in loss of power in the engine.
  • Acrid smoke – oil leaks due to bad head gasket can get in contact with hot exhaust and cause a burnt, acrid smell.
  • Messy coolant or oil leaks on the ground – liquid droplets (dark brown or yellowish) can mean leaks due to worn-out gaskets and seals.
  • Bubbles in the coolant – if compressed gasses have escaped into the radiator via a failed head gasket, you can confirm this by checking the radiator. First open the radiator cap, start the car, and check the coolant. The presence of bubbles indicates a blown head gasket.

Learn to use your senses to troubleshoot car issues and identify symptoms due to a bad cylinder head gasket. 

What causes blown head gasket?

  • Repeated overheating - Head cylinder gaskets rarely cause problems, but negligence on you part can cause issues. Once you notice your car overheating, don’t ignore it. Check your cooling system for possible issues, such as a leakage or frequently low level of coolant. 
  • Continuing to drive an overheated car – When you’re on the road and your car overheats, pull to the side of the road, and let your car cool down before you refill the radiator. 
  • Inferior head cylinder gasket material – some other times, it’s not negligence on your part. The fault could be in the low-quality gasket material or design. If you’re replacing the gasket, make sure you use one that is made of multiple-layer steel so that you won’t need to prematurely replace it again in the future.    

Troubleshooting a Blown Head Gasket

Can you DIY a cylinder head gasket replacement? 

Yes, you can, just make sure you know what you’re doing. Replacing a part like this is no simple task. It takes a lot of work to do, as it is an intensive part of the engine. The good thing about head gaskets is that they rarely break down. It means that replacing them is not a frequent issue.

If for some reasons, your car’s cylinder head gasket does need replacing and you cannot bring it for servicing yet, here are the general steps:

  • Disconnect the car battery to avoid short-circuiting. 
  • Drain the engine of any medium like oil or water.
  • Remove the components of the broken head gasket. It is best to use a manual to do this part to avoid removing or losing pieces.
  • Insert the new cylinder head gasket, also using the help of a manual to guide you in reassembling it. Make sure to clean all the parts as well. 

Here are some things to keep in mind: 

  • When you disconnect the parts, do not disturb any other component of the engine. 
  • When you reassemble the new head gasket, tighten all the pieces in place. If one comes loose in the future, it could cause problems for your engine.
  • Detecting the problem in the gasket at an early stage will help you avoid high-cost engine issues in the future. Get a professional, as much as possible, to do the necessary repair. 

How to fix blown head gasket without replacing it

You might be wondering – Is it expensive to replace a blown head gasket? Well, the head gasket replacement part is not that expensive, but the labour cost that goes with it is because it takes a lot of work to do.  

If the problem is not fully blown and you can’t get your car to a mechanic just yet, you can try a temporary fix.

If for some reasons you cannot completely fix a burst head cylinder gasket, here's a quick fix to keep your car running a few more kilometres. 

Chemical gasket sealers are available, and you can use one to DIY-repair a blown head gasket issue. Follow the instructions on the product label. 

Not every case of burst head gasket can be solved by this temporary fix, though. So, if overheating persists, head on to the nearest service station. 

There you have it – what you need to know about your car's cylinder head gasket and how to fix it.

Check out this article if you suspect a cracked cylinder head issue.