|One hot problem
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.
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
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.