Why Head Gaskets Fail


The failure of a head gasket is a car owner’s worst nightmare. It means that the head gasket is either leaking compression or leaking coolant into the crankcase. Both of these scenarios are pretty bad. If the head gasket is leaking compression, then the car will lose its fuel economy and the spark plugs may begin to misfire. If the head gasket is leaking coolant, then this coolant can enter the crankcase and ruin the bearings very quickly. In either case, the owner is looking at a pretty hefty repair bill to have the problem remedied.

Before we can go over the most common reasons that head gaskets fail, we need to know what a head gasket is and what role it plays in the proper operation of your vehicle. In an internal combustion engine, the head gasket is a gasket that sits between the engine block and the cylinder head. Its primary role is to seal the cylinders from oil or coolant leaking into the cylinders, and to make sure that the engine maintains proper compression. Therefore, its role in you car’s engine is critical to the proper combustion of gasoline. Now that we know what a head gasket does, we can now explore the reasons that they fail. There are numerous reasons for the failure of the head gasket, but some reasons are more prevalent than others.

Poor Installation of the Head Gasket

A likely culprit for the failure of the head gasket is poor installation. The head gasket is held securely to the engine block by its head bolts. If these bolt are not tightened down correctly, then the head gasket will not have the seal that it needs to operate properly. Another thing that should be considered is that the gasket may have been installed with the wrong type of sealant applied to it. It is quite possible that the wrong type of sealant can cause a chemical reaction to occur on the gasket, thus speeding up its deterioration. This is especially true when the head gasket is composed of a composite material such as graphite.

Spark Knocking or Spark Plug Misfires

The functioning of your engine can have a dramatic impact on the head gasket. A primary cause for head gasket failure is a spark plug knock. This is caused when the fuel in the cylinder is ignited too soon by the spark plug. This makes the engine sound like it has a bunch of loose marbles banging on its interior. A spark plug knock is usually caused by a malfunctioning EGR valve, but other factors such as a fuel/air mixture that is too lean can cause this problem as well.

A spark plug misfire, also caused a detonation, occurs when the gasoline in the cylinder is ignited by something other then the spark plug. This condition can occur if there are hot-spots in the chamber that ignite the fuel before the spark plug has a chance to do its job. Usually this condition can be caused by an engine that has too high of a compression, but there are other culprits as well. It can be caused by using cheap gasoline or gasoline that is the wrong octane, by using the wrong type of spark plugs, or the failure of the EGR valve.

Overheating of the Engine

The main reason that a head gasket fails is overheating of the engine. When an engine is allowed to overheat, then the engine block and the head gasket expands. While both the head gasket and the engine is designed to resist some increases in temperature, a rapid increase in temperature can cause the head gasket to fail. This is usually caused by the failure of a thermostat or one of the radiator hoses. Failure to replace one of these inexpensive parts can lead to a repair that cost thousands of dollars.

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