Why does a head gasket fail?The most common cause of a blown head gasket is engine overheating. When the engine gets too hot, the cylinder head expands (thermal expansion), which can crush the head gasket and cause failure.
Once a head gasket has failed it can cause all manner of problems, including:
1- An overheating engine
Hot exhaust gases can leak into the cooling system, or coolant can leak into the cylinders and be burnt off as steam. Either way, the result is an overheating engine.
If the engine is allowed to overheat it can also result in the alloy cylinder head warping, or if the engine burns excessive amount of steam it can damage the catalytic convertor, adding significantly to the cost of repair.
2- Loss of power
3- Oil contamination
Can a head gasket cause an oil leak? Not exactly, but when a head gasket fails it can allow the coolant and oil to mix, resulting in contaminated oil that will ruin the engine’s bearings if left unattended. If anything, the oil-coolant contamination will cause the engine oil level on the dipstick to rise.
Repair requires a complete engine oil flush as well as a replacement oil filter to ensure all traces of contaminated oil are removed from the engine.
The same failure can also cause exhaust gases to enter the oil-ways and pressurise the crankcase, causing lubrication issues and excessive engine wear.
5 External leaks
This may not manifest itself as an immediate problem (other than causing a mess) but if the coolant or oil levels are allowed to drop too far it can lead to serious engine issues.
How can a head gasket be repaired?
But if the job can go ahead, everything is bolted back together, which includes replacing the timing belt or the chain (if necessary).
Are head gasket sealers any good?
How long does it take to fix a head gasket?
How much does a new head gasket cost?
How to prevent head gasket failure
Ensure the system has no leaks, the radiator is working efficiently and the coolant is topped up to the correct level. Also, make sure electric fans are working correctly, and that the thermostat opens at the temperature it should.
If you suspect a head gasket failure you can test for carbon dioxide in the cooling system. This test will show if the compression has leaked into the cooling system, and therefore if the head gasket has blown. However, it won't show if there are any other problems with the head gasket, so the absence of carbon dioxide in the cooling system does not guarantee a healthy head gasket.
Some head gaskets can just fail because they are of a poor design and are not robust enough for the application. Thankfully MLS (multiple layer steel) replacement gaskets are available for most applications and offer improved reliability over the original gasket design.