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Question : MY 2003 Proton Wira 1.5GLi was found to have a leaking cylinder head gasket after I complained to the workshop about loss of engine power. I was then advised to have the cylinder head removed, get an engine top overhaul and replace the gasket. How could the cylinder head have failed so fast? My car has never overheated and it has only travelled 55,000km since new.

Answer : ALTHOUGH overheating is the main cause of cylinder head problems, this is not always the case. Cylinder head gaskets perform under tremendous stress and any weakness in or around the gasket area is likely to result in failure.

The most obvious cause of overheating is when the cooling system fails, resulting in a significant rise in engine temperature, which leads to cylinder head distortion in the engine block.

Similarly, lack of lubrication, especially to the top-end of the engine, can result in localised overheating, resulting again in cylinder head distortion. Modern cylinder heads are made of cast aluminium, which distorts easily when heated unevenly.

The last and least obvious cause of over- heating is the result of detonation, pre-ignition or pinging. Pinging is caused by the use of an incorrect (low) grade fuel, or if incorrect heat grade (too hot) spark plugs are used.

Pinging can raise the internal temperature of the engine to a point that can result in meltdown of the piston crowns. Irrespective of the cause, renewal of the gasket is the only solution. When the cylinder head is removed from the engine, the mating surfaces between cylinder head and gasket must be checked for distortion, and if any is found, the surface(s) must be machined to restore its flatness.

Very often, cylinder head gaskets have been found to leak, yet no distortion or overheating is evident. In such cases, the cause of the leak can merely be put down to a manufacturing fault in the gasket in the first place.


Metal head gasket

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