Toyota-Lexus-Subaru-Honda Head Gasket

The head gasket serves to seal off the combustion chambers and the cooling system from each other and also from the rest of the world. An early sign of internal failure is an invisible loss of coolant that doesn’t appear to be a result of any external leaks. In this case the coolant enters into the combustion chamber and passes out the exhaust.

As it gets worse, it will be accompanied by excessive white steam out the exhaust, and you may also notice that the engine seems to run rough with a misfire on initial startup after sitting. If enough coolant accumulates in the cylinder while sitting it can even result in a “hydrostatic lock” where the engine can’t crank due to the fact that the coolant can’t be compressed. A blown head gasket can be detected at a shop by using an exhaust analyzer to sniff the cooling system for HC’s (unburned hydrocarbons) that are there as a result of exhaust from the combustion forcing it’s way past the head gasket and into the cooling system.

A blown head gasket can result in overheating, both from loss of coolant and from the cooling system being made less efficient due to the exhaust gasses interrupting the flow of coolant through the engine. Alternatively, a good head gasket can be blown in relatively short order due to excessively overheating the engine as a result of some other cause, such as loss of coolant from some other leak, a bad thermostat, a restricted radiator, a bad water pump, or a broken water pump drive belt.

When the head gasket is blown as a result of overheating, the cylinder head is quite commonly warped at the same time. In addition to head gasket failure resulting in damage to the engine through overheating, it also risks scoring and damaging the cylinder walls as the mix of antifreeze and water strip the lubrication from the cylinder walls. This can result in the engine burning oil, as the rings are no longer able to keep the oil from slipping between the rings and the cylinder walls. If you suspect that you may be experiencing a head gasket failure, I encourage you to have it checked and repaired directly, as delayed action may eventually result in catastrophic engine failure.