Head gasket guide

Signs of head gasket failure

Can you repair a head gasket and is it worth fixing?

The head gasket is a key part of your car’s engine and helps to keep everything running smoothly.

If your gasket fails or “blows”, it can cause problems in your car’s ability to run normally, so it’s important to know how to check whether your gasket is functional and secure before your car breaks down. For peace of mind, you can always get breakdown cover with us.

If you find your head gasket is damaged, you should talk to an expert to get it repaired as soon as possible and save yourself trouble in the long run.

In this article

Cylinder head gasket

What is a head gasket?

A head gasket is a seal that prevents motor oil or coolant leaking into your engine cylinder chambers, as well as preventing the gases from escaping them. It’s a crucial part in ensuring your car runs smoothly.

Leakages can cause the engine to run poorly or overheat, potentially creating problems with the car’s ability to run and causing damage over the long term.

These leakages tend to occur due to damage to the gasket – usually called a “blown gasket”.

What are the signs of a blown head gasket?

These are the blown head gasket symptoms that you should look out for:

  • Loss of engine power – you might start noticing problems while driving before anything else. Pressure in the combustion chamber will decrease, and so will your engine power.
  • Overheating engine – your engine may start overheating regularly due to the loss in coolant.
  • White exhaust smoke – evaporating coolant that’s leaked into the combustion chamber may cause visible white exhaust smoke.
  • Smell from exhaust – a sweet smell from your exhaust, or water dripping out, can be a sign of leaks.
  • White oil from a head gasket leak – when checking your engine oil, if you notice a milky or white colour on the dipstick or around the filler cap, that can be a sign of leaking coolant.
  • Testing a head gasket – you can try a pressure test of your cooling system, though it's best to get this done at a garage.

Keep an eye out for these blown head gasket symptoms in order to keep your car running safely and securely. If you think you have a blown head gasket and aren't currently a member, don't worry, we can still help you with instant breakdown cover.

If you break down, we'll get you back on the road

What causes a blown head gasket?

The most common cause of head gasket failure is overheating which can cause damage, but pre-ignition issues can also lead to leaks if the fuel is combusted at the wrong time.

Faulty head gaskets are more likely to occur if they’re poor quality or haven’t been installed correctly – a seal shouldn’t be too tight or too loose as both can result in problems.

How to prevent a blown head gasket

As blown head gaskets are often the result of overheating, you’ll want to make sure that engine coolant is topped up to the right level – the coolant system itself should also be in smooth working order with no leaks. Find out how to check your engine coolant so that you’re on the safe side.

You’ll also want to make sure that your head gasket is of a high quality and properly installed/sealed. If you’re worried about this, a garage can check for you. As above, you’ll want to make sure that the seal isn’t too tight or too loose.

Can you drive with a blown head gasket?

It’s not recommended to drive with a blown head gasket as pressure in the combustion chamber reduces and the engine will lose a great deal of power.

There’s also a higher chance of overheating, which can cause more damage to your engine. The same applies if your motor oil and coolant leak into one another and stop lubricating properly.

It's possible to drive for short distances, but it should be avoided if at all possible to prevent more severe damage to your car.

How long can you drive with a blown head gasket?

If you absolutely need to drive for short periods with a damaged head gasket, try using head gasket sealer first to protect your engine. However, driving should be avoided if at all possible to prevent more severe damage to your car.

Can you fix a blown head gasket without replacing it?

Head gasket sealers may work as a temporary fix on developing issues if the problem is caught early enough. But they shouldn’t be relied on as a long-term repair.

Some sealers also leave evidence in the cooling system like metallic flecks, which is a sure sign there has been a head gasket problem. These can be difficult to get rid of, even after a proper repair has been done.

Find out and fix the problem with an expert vehicle check from AA Smart Care.

What is the seal for a head gasket?

Sealant can be used to repair a head gasket which is slightly damaged and beginning to lose compression. By using a sealant, you can stop coolant and oil from leaking into the cylinders. Sealants for head gaskets can really work, but you need to make sure you’re using the correct amount for your engine.

For example, an engine with 4 or 6 cylinders will need less sealant than an engine with 10 cylinders. Sealants for head gaskets can differ in quality – so make sure you’re picking up a decent one.

How does the head gasket sealer work?

If you’re using a sealer, you should always check the instructions first as different products can vary.

Generally the following steps are taken when a head gasket sealer is used:

  • Head gasket sealer is added to the cooling system
  • The engine is run until it reaches operating temperature.
  • The sealer circulates the system and particles react when they come into contact with the damaged areas, blocking small cracks and leaks.

Can you use head gasket sealer to replace it?

Head gasket sealers are usually only a short-term fix – at some point (ideally sooner rather than later), you’ll want to get your engine checked over by a mechanic. If your head gasket has underlying damage, then it will eventually break the sealant and cause bigger problems.

How much does it cost to replace and repair a head gasket?

Your head gasket repair cost could be expensive, more because of the cost of the labour than the cost of the head gasket itself.

The repairs usually cost upwards of £500 and might be a lot more, but if you don’t get a head gasket replacement, this may result in additional damage and higher repair costs – or even permanent damage to the engine.

Head gasket sealer can be a lot more affordable – often less than £50 – but it only offers a temporary fix and shouldn’t be relied on as a long-term repair.

That’s why it’s best to speak to an expert if you have any problems with your head gasket.

Are head gaskets expensive?

Head gaskets themselves are generally inexpensive, but the labour required to replace them is significant and often costs as much as £1000. The best way to keep costs down is to stay on top of your car’s health, get it checked and maintain it regularly. You can also buy breakdown cover with Parts and Garage cover, which will help cover the costs of repair/replacement work carried out at a garage.

Is a head gasket worth fixing?

If you don’t repair a blown head gasket, your engine can incur significant damage, starting with loss of engine power and ultimately leading to complete engine failure. Over time, your engine will overheat (one of the top 10 breakdown causes) due to exhaust gases clogging up the cooling system, so make sure to prioritise getting your head gasket fixed.

Published: 20 July 2021 | Updated: 28 November 2023 | Author: The AA