A head gasket is a shaped piece of metal and composite that costs less than a tank of fuel. Replacing one costs north of a thousand pounds, because the top of the engine has to come apart to fit it. It is also the one repair on this site where the quote can grow after work starts — and there is a good reason for that.
| What you are paying for | Typical range |
|---|---|
| Parts — gasket set, bolts, fluids | £150 – £400 |
| Labour — 8 to 14 hours at £100/hr | £800 – £1,400 |
| Typical total | £950 – £1,800 |
Independent garage rates, assuming the head is reusable. Skimming or a replacement head adds to this. See the full list in our Repair Costs Hub.
How much does a head gasket cost?
£950 to £1,800 at an independent garage on a four-cylinder engine where the head turns out to be reusable. A V6 or V8 with two heads is roughly double, because it is two of the same job.
Look at the split. The gasket set and head bolts are £150 to £400. Everything else is eight to fourteen hours of taking the top of the engine apart, having the head checked and refitted, and putting it back together with new fluids and a proper bleed.
That labour is not padding. Inlet and exhaust manifolds off, camshafts and timing components out, head bolts released in sequence, head lifted, both faces cleaned to a specific standard, head checked for flatness, then everything rebuilt with new bolts torqued in stages and the cooling system bled properly. Rushing any of it is how the job gets done twice.
The five symptoms
- White smoke from the exhaust with a sweet smell. Coolant getting into a cylinder and being burnt. The most recognisable sign.
- Coolant disappearing with no leak underneath. If you are topping up and the driveway is dry, it is going somewhere internal.
- A mayonnaise-like residue under the oil filler cap or on the dipstick — coolant and oil mixing. Note that a light film can just be condensation on a car doing short trips; a thick beige paste is not.
- Overheating, particularly a temperature gauge that climbs when working hard and settles when cruising.
- Bubbles in the expansion tank with the engine running, or the tank pressurising quickly. Combustion gases getting into the coolant.
A garage can confirm it in minutes with a combustion leak test — a chemical that changes colour in the presence of exhaust gas in the coolant — or a cylinder leak-down test. Insist on one of those before agreeing to the work. Several of these symptoms can also be a cracked head, a failed oil cooler or a leaking inlet gasket, and those are different jobs.
Why the price can go up mid-job
This is the part worth understanding before you say yes, because it catches people out and it is nobody's fault.
Nobody can see the condition of the cylinder head or the block face until the head is off. Once it is, three things can change the number:
- The head is warped and needs skimming — a machine shop cost, usually modest, plus time.
- The head is cracked and needs replacing. That is a large step up, and on some engines a used or reconditioned head is the sensible answer.
- The engine has been run hot for too long, and there is bore or piston damage below. At that point the conversation changes to a replacement engine.
A good garage will tell you upfront that the quote assumes a reusable head and will come back to you with photographs and a revised figure if it is not. Ask for exactly that before work starts, and ask what skimming would add. It turns a nasty surprise into a known risk.
It is also why continuing to drive an overheating car is such an expensive decision. The difference between stopping at the first temperature warning and carrying on for another twenty miles is frequently the difference between this repair and a new engine.
What actually causes it
Head gaskets rarely fail on their own. They fail because the engine got too hot, and something else made it too hot:
- A failed thermostat stuck closed.
- A water pump that has stopped circulating.
- A radiator blocked internally, or a cooling fan that has stopped working.
- A slow coolant leak nobody topped up.
- The last head gasket job done without the head being checked for flatness.
Which leads to the important question to ask your garage: what made it overheat? Fit a new gasket without fixing the cause and you will be back. A proper job includes finding and fixing whatever cooked it.
Is it worth repairing?
Honest arithmetic. The repair is £950 to £1,800, possibly more if the head needs work. So:
On a car worth £1,500, it is usually not worth it — unless the rest of the car is genuinely sound, you know its history, and you would otherwise be spending £4,000 on a replacement of unknown provenance.
On a car worth £5,000 or more with a good history, it almost always is. A properly done head gasket on an otherwise healthy engine is a permanent repair, not a patch.
One thing to avoid: the sealant products sold in a bottle. On a hairline seep they occasionally buy a few weeks. On a failed gasket they do nothing except circulate through the cooling system and block the radiator and heater matrix, which adds to the bill. No garage will thank you, and a buyer who finds sealant residue will walk away.
Is a head gasket covered by a warranty?
The gasket itself is a listed component on most levels of independent cover. But head gasket claims are scrutinised more than most, and it is worth knowing why.
Because overheating is the cause, an assessor will want to establish what caused the overheating and whether it was allowed to continue. A car driven with the temperature gauge in the red, or run low on coolant over months, points towards a failure to maintain the vehicle rather than a component simply failing — and every UK warranty excludes damage caused that way.
That is not a technicality invented to avoid claims; it is the difference between a part that broke and a car that was driven until something broke. In practice it means two things for you. Stop at the first temperature warning, and keep your servicing and coolant top-up evidence.
Where a covered component caused the overheating — a water pump or thermostat failing, for instance — the head gasket damage that followed is a what isn't covered question, and worth asking about before you need the answer.
ClearPath takeaway
Get it confirmed with a combustion leak test before anyone takes an engine apart. Several cheaper faults produce the same symptoms.
Ask two questions when you accept the quote: what will it add if the head needs skimming, and what caused the overheating. A garage that answers both clearly is the one to use.
And the cheapest advice on this page: if the temperature gauge climbs, stop. Not at the next junction — as soon as it is safe. That decision is worth thousands.
