Head Gasket
What it does
Seals the junction between the engine block and cylinder head, keeping coolant, oil and combustion gases properly separated.
Possible failure symptoms
Persistent white exhaust smoke (often with a sweet smell) that doesn't clear once the engine is warm, coolant and oil mixing (a milky substance on the dipstick or under the oil cap), engine overheating, or coolant loss with no visible external leak. A little white vapor on a cold start, or some residue under the oil cap after short trips in cold weather, can be normal condensation — which is why a proper test matters before assuming the worst.
Potential consequences
A failed head gasket can quickly lead to engine overheating and, if driven on, serious internal engine damage.
Typical repair process
A technician confirms the diagnosis, often via a combustion leak test, then removes the cylinder head, replaces the gasket, and inspects the head and block surfaces for damage before reassembly.
Parts involved
The head gasket, related seals, and often new head bolts; the head and block are inspected for warping.
Questions to ask a mechanic
Ask how the diagnosis was confirmed, and whether the cylinder head was checked for warping — resurfacing or replacing a warped head is sometimes needed alongside the gasket.
How coverage generally treats this
General guidance about how these categories typically work — not a claim about your own coverage.
Manufacturer warranty
Potentially covered under bumper-to-bumper coverage while active, and typically covered under powertrain coverage as an internal engine component if the warranty is still active.
Powertrain coverage
Typically included, since the head gasket is an internal engine component and engine coverage is a core part of most powertrain definitions.
Exclusionary service contract
Usually covered under exclusionary contracts and most named-component plans that include the engine, since it's a common and often expensive failure point — always confirm against the specific contract.
Auto insurance
Ordinary mechanical failure or wear is normally not covered by standard auto insurance.
Manufacturer recall
Only applicable if there's an open recall for a specific head gasket or engine defect.
Related warning lights
Noticing a related symptom on your own vehicle? The Symptom Explorer shows what other owners of your specific year, make and model have reported to NHTSA.
This is general guidance, not a diagnosis or a repair-cost estimate — we don't have reliable cost data, so none is shown here. A qualified technician should confirm the actual cause and cost for your vehicle.