The head gasket is an essential part of an internal combustion engine. It sits between the cylinder head and the engine block, and has two important roles:
Firstly, the combustion process produces high-pressure gases which give the engine its power. The gasket makes sure that all the pressure stays within the combustion chamber, where it’s needed.
Then, the head gasket makes sure that the engine oil and coolant from the engine block don’t leak and mix together.
If the head gasket fails (otherwise known as a blown gasket), your engine can overheat, lose power, or even suffer irreparable damage. Repairing or replacing your head gasket can be expensive, so it’s important to check it regularly and address any issues immediately.
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Common causes of head gasket failure
One of the most common reasons for head gasket failure is the engine overheating. This may be caused by:
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Issues with the cooling system.
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A faulty radiator.
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A broken thermostat.
High temperatures can warp the engine block and cylinder head, meaning the gasket can’t form a secure seal. The heat can also crack, puncture or warp the gasket itself.
When the pressure in the engine block is too high, this can cause the head gasket to fail. This may occur when air and fuel in the combustion chamber ignite before they’re supposed to (known as pre-ignition), putting extra stress on the gasket.
Other reasons for head gasket failure include incorrect installation (e.g. bolts tightened too much), as well as general wear and tear.
Signs of a blown head gasket
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Your engine temperature warning light illuminates.
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You notice a burning smell coming from the engine.
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You hear clicking or clanking sounds.
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If your coolant constantly needs topping up or is visibly leaking, this could signify that the head gasket isn’t forming a seal anymore.
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If coolant gets into the combustion chamber, it will burn off and produce white smoke from the exhaust, which may have a sweet smell.
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You might also notice water dripping from the exhaust.
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Check your oil. If you discover it’s milky or white, this is a sure sign that coolant has mixed with the oil and emulsified.
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If combustion gases get through a blown gasket, you’ll notice bubbles in your radiator when you take the cap off.
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Finally, if the head gasket has blown, acceleration and engine power will be reduced.
Is it worth repairing or replacing a head gasket?
Before you decide whether it’s worth repairing or replacing your head gasket, think about your car’s age, mileage and overall condition.
If your car has a high mileage and considerable wear, then the cost of repair or replacement may exceed the car’s actual value. To find your car’s value, enter your reg and mileage into our free car valuation tool. Don’t forget to declare any damage and your car’s history for a comprehensive valuation.
It wouldn’t be cost-effective to fit a brand-new part in an old engine that’s near the end of its life. However, if your car is in good condition, repair or replacement could get you back on the road and keep you there for a long time to come. So, which one should you go for: repair or replacement?
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When to repair
Repairing the head gasket is much cheaper than completely replacing it - or the entire engine. It also takes much less time. However, this is only appropriate when the damage is minor.
You should also bear in mind that the head gasket may need further repairs or replacement at a later date.
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When to replace
Head gasket replacement is much more expensive - and takes longer, but it’s the only option to remedy severe damage to the gasket or engine. The good news is, your replacement head gasket should last for a long time, if it is installed correctly.
Replacing a head gasket is a big job and therefore, should only be carried out by a professional mechanic, or someone with extensive knowledge and experience. If you try to replace it yourself and make a mistake, you could damage your engine and compromise your car’s safety.
Head gasket replacement costs
Typical costs for head gasket replacement range from £700 to £1,850. Here are the average head gasket supply and installation costs for some of the most popular car brands in the UK:
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Audi: £1,170
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BMW: £1,150
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Ford: £850
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Honda: £950
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Land Rover: £1,850
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MG: £1,350
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Mercedes-Benz: £1,500
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Nissan: £700
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Peugeot: £1,050
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Saab: £1,000
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Suzuki: £700
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Toyota: £700
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Vauxhall: £1,100
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Volkswagen: £975
Please note: These figures are for illustrative purposes only. Contact your local garage for a precise quote.
Whilst your car’s brand and model will likely influence how much you’ll pay for head gasket replacement, there are other factors to consider, including:
Hourly labour costs: While the gasket itself is a relatively inexpensive part, replacing it can take up to 10 hours. This is a fairly complicated process, so you’re also paying for the mechanic’s skill and expertise.
Hourly labour rates will also vary depending on the location of the garage. For instance, according to a survey from industry news site Garage Wire, the cheapest area for garage labour is Huddersfield (averaging £47 per hour) - and South West London is the most expensive (averaging £141 per hour).
Local automotive market: The garage’s location will also influence how difficult and costly it is to source the required part(s).
Complexity of the replacement: Additional costs may apply if the mechanic has to flush the oil and coolant systems, replace other parts of the engine (such as the water pump or thermostat), or simply inspect the engine for other issues.
Tips for reducing head gasket repair costs
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Looking after your head gasket is the best way to make sure you don’t end up shelling out for repair or replacement.
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Get your car serviced at the intervals recommended by the manufacturer. If you spot any issues between service intervals, take your car to a mechanic promptly.
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Stay on top of routine maintenance (e.g. checking fluids). This will help you spot any developing issues before they become major problems.
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Use high quality coolant and top it up when needed. Check for leaks, too – and if you do find any, get them fixed straight away.
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Drive smoothly and steadily, avoiding aggressive acceleration.
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Make sure you warm up the engine before driving, so that the oil and coolant can circulate properly. Cooling down is also important.
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As soon as you notice the first signs of a failing head gasket, take your car to a garage. This could help you avoid a hefty repair bill.
Frequently Asked Questions
Whether it’s worth fixing a blown head gasket depends on the age, mileage and condition of your car, as well as the extent of the damage. Replacing the gasket will be a better option if the damage is severe.
Changing a head gasket is a fairly complex task that should only be carried out by a professional mechanic or someone with considerable experience.
Replacing the head gasket is likely to increase the lifespan of your engine, as long as you drive correctly and keep up with maintenance.
Head gasket sealers can work in some cases by temporarily plugging any holes in the gasket. However, this isn’t considered a long-term fix, so you should take your car to be checked over at your local garage as soon as possible.