Mercedes A-Class head gasket cost
fitted at an independent garage · gasket set, new head bolts, skim, fluids and labour included
- Diagnosis first £60–£100
- Typical time 8–12 h
- Dealer +50%
A Mercedes A-Class head gasket costs £750–£1,350 fitted at an independent garage, with diagnosis at £60–£100 and 8–12 hours of labour. That diagnosis is worth more on this car than on any other in our table, and for a specific reason: the A-Class cooling system has an unusually long list of places coolant can escape from, several of which leak internally and leave nothing on the ground. “Losing coolant with no visible leak” is a famous head gasket symptom. On this car it is also the symptom of at least six cheaper things. Compare against every model here.
A-Class head gasket costs by job
| Job | What it involves | Fitted cost (independent) |
|---|---|---|
| Diagnosis first | Block test for combustion gas in the coolant, a cooling-system pressure test, and a systematic check of the known external and internal leak points below | £60 – £100 |
| Head gasket replacement | Full head set, new single-use stretch bolts, machine-shop pressure test and skim, fresh coolant and oil | £750 – £1,350 |
| With a condemned head | When the head will not skim true or the pressure test finds a crack | Add £300 – £800 |
| Main dealer | The identical job at franchise labour rates | About 50% more |
Ranges match our head gasket cost guide row for the A-Class. Estimates assume the head skims within tolerance.
The cheaper leaks to rule out first
Start with the ones that leave evidence. The water pump, the thermostat housing, the coolant housing near the exhaust gas recirculation cooler and the fuel filter housing with its water outlet are all documented sources of coolant loss on these engines. Some weep only when hot and pressurised, which is why a cold inspection on a driveway finds nothing and a workshop pressure test finds them in minutes. The expansion tank and its cap belong on the same list — a tank that will not hold pressure lets the coolant boil early and disappear as vapour, with no puddle to explain it.
Then the two that leak internally, which is where owners get caught. The oil cooler shares a boundary with the coolant, so when it fails the expansion tank fills with oil — dramatic, alarming and nothing to do with the head gasket. And on the newer cars there is a documented internal leak in the charge air cooler, which lets coolant pass into the intake system: a slow, steady loss with no external trace at all, exactly imitating the classic gasket symptom. Neither can be found by looking under the car, and neither costs anything like the figure at the top of this page.
There is also a manufacturer angle worth using. A service action exists covering a coolant connection at the cylinder head on some of these engines — and it was not proactively communicated to every owner, which means cars are still driving around unaware they qualify. Before you pay anyone, ask a franchised dealer to check your VIN against outstanding actions. It is a free phone call, and on this car it is the single highest-value question on the page.
Why diagnosis is worth more here than anywhere
On a supermini, the arithmetic of testing before spending is straightforward: a small sum protects a larger one. On the A-Class it is sharper still, because the repair being protected is £750–£1,350 — the top of our table — and the list of alternatives is longer. A £60–£100 diagnosis that finds a housing, a cooler or a cap has not just saved money; it has replaced a two-day engine strip with a workshop afternoon.
Which produces a specific question to ask, and it is not the usual one about block tests. It is: “which of the known leak points have you actually checked, and was the charge air cooler among them?” Any competent workshop will run a block test. Far fewer will systematically work through the internal leak paths on this particular car before concluding it must be the gasket, and the difference between those two garages is the whole cost of this page.
If the block test does come back positive, that is a real answer and the repair is the right response — but insist on the machine-shop pressure test on the removed head before the final figure is agreed, because the +£300–£800 branch is where an A-Class bill stops being comfortable. And if it lands there, run the numbers properly rather than in stages: our worth-it calculator applies the half-the-value rule, which on a car of this age and badge can go either way.
Where the labour goes, and who should do it
The 8–12 hours in the table is the longest window in our range, and it is a packaging story rather than a complexity one. There is more to remove before anything interesting is reachable, more of it is fragile plastic that does not enjoy being disturbed twice, and the reassembly has more to go back in a specific order. That is also why the gap between two quotes can be wide: at this many hours, a £20 difference in hourly rate is worth more than the entire gasket set.
You do not necessarily need a franchised dealer for the repair itself. What you need is a workshop that lifts heads regularly and has a machine shop it works with — the same test that applies to every car on this site. Where the dealer is genuinely worth a visit is earlier: the VIN check above, and any goodwill conversation, both of which have to happen before an independent starts work rather than after. Our independent versus dealer guide covers the wider trade-off.
One caveat specific to the diesels: coolant contamination on any diesel deserves a look at the exhaust gas recirculation cooler before the head comes off, and the engine in the smaller A-Class diesels is not a bespoke Mercedes unit at all — a detail with real consequences for parts prices, set out on our A-Class cambelt page.
One thing to bring with you to the garage, because it narrows the list faster than anything a workshop can do. Note whether the loss happens while the car is being driven, while it sits, or both — a system that loses coolant overnight without moving points somewhere quite different from one that only drops on a long run. Owners who can answer that question have already done part of the diagnosis, and on a car with this many candidates it is a genuinely useful head start.
Worked example — A-Class diesel, head gasket, head skims true
Head set and new stretch bolts £210 · machine shop pressure test and skim £95 · labour 10 hours at £70 £700 · coolant, oil, filter and thermostat £95 · total ≈ £1,100 — inside the £750–£1,350 range above. For comparison, several of the leak points described earlier are resolved for a small fraction of this, which is the entire argument for spending £60–£100 first.
FAQ
How much does a Mercedes A-Class head gasket cost in the UK?
£750–£1,350 fitted at an independent garage, including the gasket set, new stretch bolts, a standard head skim and 8–12 hours of labour. Diagnosis costs £60–£100 first. A head that will not skim true adds £300–£800, and a main dealer charges roughly 50% more.
Where does coolant usually leak from on a Mercedes A-Class?
There is a long list before the head gasket: the water pump, the thermostat housing, the housing near the exhaust gas recirculation cooler, the fuel filter housing water outlet, and an expansion tank or cap no longer holding pressure. Several only weep when hot, so a cold inspection misses them entirely.
Can a charge air cooler leak coolant and imitate a head gasket?
Yes, and it is the most convincing impostor on this car. An internal leak in the charge air cooler passes coolant into the intake system, producing a slow steady loss with no external trace — exactly the symptom that sends owners searching for head gaskets. It cannot be found by looking underneath the car.
Is oil in the coolant tank always a head gasket on an A-Class?
No — the oil cooler shares a boundary with the coolant, and when it fails the expansion tank fills with oil. It looks alarming and reads like a catastrophic gasket failure, but it is a different component with a very different bill. It needs to be ruled out before any head-off work is agreed.
Is there a Mercedes service action for coolant loss?
A service action exists covering a coolant connection at the cylinder head on some of these engines, and it was not proactively communicated to every owner. Ask a franchised dealer to check your VIN against outstanding actions before paying for any repair — it costs nothing and occasionally changes everything.
Why is diagnosis more important on an A-Class than on a smaller car?
Because the repair it protects is larger and the list of cheaper alternatives is longer. £60–£100 spent testing can replace a two-day engine strip with an afternoon’s work on a housing or a cooler, which is a better return than the same spend on almost any other car in our table.
Do I need a Mercedes specialist for an A-Class head gasket?
Not for the repair itself — you need a workshop that lifts heads regularly and works with a machine shop. A franchised dealer is worth a visit earlier, for the VIN check on outstanding actions and any goodwill conversation, both of which have to happen before an independent starts work.
Why does an A-Class head gasket take 8 to 12 hours?
Packaging rather than difficulty. There is more to remove before the head is reachable, a good deal of it is fragile plastic that does not survive being disturbed twice, and the reassembly sequence is longer. At this many hours the hourly rate matters more to the final bill than the parts do.