Head Gasket Failure — The Symptoms and Why It Matters

8 May 2026 · 6 min read

What the head gasket does

The head gasket seals the joint between the engine block and the cylinder head, keeping the combustion pressure, the coolant, and the oil in their own separate passages. It works under extreme heat and pressure, and when it fails those fluids and gases start to mix where they should not.

A head gasket can fail in different ways — letting combustion gases into the coolant, coolant into the cylinders, oil and coolant to mix, or pressure to escape. Each produces slightly different symptoms, but all need prompt attention.

The warning signs

The common signs are the engine overheating or the temperature gauge rising, white sweet-smelling smoke from the exhaust, coolant disappearing with no visible leak, and bubbles in the coolant header tank as combustion gases enter the system.

A tell-tale milky residue under the oil filler cap or on the dipstick means oil and coolant are mixing. Rough running or a misfire can appear if coolant is entering a cylinder. If you spot these, stop driving — running on makes the damage far worse.

How we test for it

We do not condemn a head gasket on symptoms alone. We carry out a combustion gas test on the coolant, which chemically detects exhaust gases in the cooling system and gives a fast, reliable answer. We also pressure-test the cooling system and check compression where needed.

Diagnosing properly first matters because overheating has other causes too — a stuck thermostat, a failed water pump, or a blocked radiator can mimic some of the same signs. We confirm the fault before recommending any strip-down work.

Head gasket work in Bilston

If your car is overheating or showing these signs, bring it to us before more damage is done. We will test it, explain exactly what we find, and give you a clear, costed recommendation.

Call Wolverhampton Auto Care on 01902 494948 or book online. We are on Hare Street, Bilston, WV14 7JW, serving Darlaston, Willenhall, Walsall and Wolverhampton.

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