In my last article I discussed a recent trip to the high country, where a mate’s Patrol overheated and blew its head gasket. The owner of the Patrol decided to fix it himself the following weekend. While fixing his car, he had a few questions as to what a head gasket actually is and how it blows.
The cylinder head gasket is the seal that joins the cylinder head to the engine block. It plays a very important role in the engine as it seals a number of different passages, as well as the combustion chambers.
Manifold and rocker cover off; the cylinder head with all parts removed, it will be ready for reassembly after a quick clean.
An engine needs oil to flow through it for lubrication, water to flow around it for cooling, combustion chambers for the ignition of the fuel-air mixture, and bolts to hold it down.
So the head gasket serves a complicated role – it not only has to be able to cope with a pressurized cooling system and a pressurized oil system, but it also has to be able to cope with extreme combustion pressures and temperatures.
It's important to remember that the most common cause of a blown cylinder head gasket is due to an engine overheating. The cylinder head on most modern vehicles is made from aluminium, and when the engine overheats the head gasket can become damaged, and in a lot of cases the cylinder head itself can bend or warp, which causes it to pull away from the gasket.
It is possible for the gasket itself to deteriorate over time, which can also cause the fault. When the gasket blows, it causes the passages to mix and in most cases will cause the combustion chamber to mix with the water passages.
the cylinder head gasket, each passage marries up to the passages within the engine block and cylinder head.
Qualified motor mechanic Adam Adler has spent half his life under the bonnet of a 4WD and has worked for some of the top accessory companies and workshops. He knows what it takes to get your vehicle out there and back home in one piece. He runs the online aftermarket store www.nutsabout4wd.com.au.