Cracked
valve
VALVE FAILURE
VALVE - CRACKED
Under certain conditions such as excessive high engine operating temperatures valve heads may crack.
Complete
pieces of the valve head will suddenly fallout. This will be accompanied by
immediate engine noise and miss-firing.
This condition is usually the result
of continued use under constantly changing conditions. (constant heavy / light
load and temperature changes). With these driving conditions careful inspection
of all valves and associated components will be necessary. Any suspect valve should
be replaced as the operating conditions are common to every cylinder.
Other valves may have cracks from the outer edge towards the centre of the
valve head. An example of a vehicle operating under these conditions could be a mail delivery van
going from full throttle to idling between each delivery.
The constant change between excessively high temperatures and normal temperatures alters the structure of the valve material and cracks begin to form. With continued use under these constantly changing conditions the valve will eventually crack so a piece will suddenly become dislodged.
Where as consistent overloaded conditions with constant high temperatures can change the valve material differently to become soft or malleable and the valve head will tulip or have a concave appearance.
: Every care has been taken in writing this information and procedures, but no responsibility can be excepted for errors, omissions or misuse of this information and procedures. The information available on this site is for your instruction only and cannot be copied for sale, © copyright 2001 UMR Engines www.engineproblem.com.au
Cracked
valve