How to diagnose and repair a blown head gasket. Car overheating, will not start? What is the cause?

Symptoms of a bad head gasket


ENGINE OVERHEATING - If the vehicle has been overheating, this can be a sign of a bad or blown head gasket. Overheating alone is not necessarily a bad head head gasket. There can be many other causes for overheating.

LOSS OF COOLANT - If the head gasket is damaged or blown, water/coolant will leak into the head. Coolant will be lost thus causing overheating.

HARD TO START - Vehicle will be very difficult to start, or not start at all. This is because the coolant is mixing with the fuel in the head. If it does start, may run normally but eventually overheat.


What to do

If the head gasket is blown to the point that the vehicle simply won't start, the head gasket will need to be replaced. This can be a very involved and costly process.

If the vehicle starts and you are losing coolant, this can be addressed by adding a sealant. This is very effective in most cases. The head gasket sealant will fill in gaps and seal the gasket. I prefer the sealant that does not require the radiator to be drained, although some sealants are better than others and seems that the sealants that require draining and flushing the radiator are a bit better.

The sealant will be added to the radiator directly when the engine is cold. This should seal the gasket. Keep in mind that eventually the head gasket will need replaced.

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hardlymoving 3 years ago from Memphis, TN

These products will give you a couple months of longevity at best. If the gasket got blown from overheating and the head is aluminum (majority of today's cars), the head is probably warped and needs to be resurfaced. Also today's head gaskets are multi-layered Stainless Steel (MLS) which allows the cylinder head and block to 'slide' against each other during heat expansion at different rates.

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