|Over the last 20 years the Motor Car Engine has evolved to a
highly engineered power plant producing power to weight ratios previously unheard of. The use of lightweight alloys
and multi-valve designs dressed with intelligent electronics and fuel injection etc gives us compact engines capable
of 150K without the thought of a decoke or rebore.
|The paralleled improvements in lubricants i.e. semi and fully
synthetic oils has furthered improved the efficiency and life expectancy of the modern car engine.
|However due to manufacturers economics and ease of long term
maintenance the cylinder head gasket remains and although vastly improved over the years, still remains a fuse
point in the event of overheating.
|The introduction of M.L.S. cylinder head gaskets, (Multi Layer
Steel), means that the aftermarket repairer must approach head gasket replacement with a whole new philosophy.
Head and block faces must be flat within 0.08mm / 0.003" and have unblemished surface finishes within 10 microns
/ 32 C.L.A. - N6. Since the M.L.S design is "unforgiving" any slight distortion, dirt, or surface blemishes
will result in a leaking gasket, be it water, oil or compression gases.
|Cylinder head bolts which are of the "stretch" design
must be renewed (any head bolt subjected to angular tightening within its tighten down procedure is deemed as a
|Some engines still employ the old composite gasket. This design
has experienced vast improvements over the years with stainless steel fire rings, silicone
beading etc. However, due to European legislation this type of gasket is now asbestos free. The substitute materials,
although good, tend to be "harder" and accordingly less forgiving than their predecessors. It is therefore
just as important, as with M.L.S. gaskets, to ensure that head and block faces are flat and that new stretch bolts
are fitted as required.
A failed head gasket is in its self a piece of forensic evidence
as to its fitting conditions. Our Technical department take seven designated measurements per cylinder bore. The
measured results indicate inherent head and block distortion percentage crush of gasket and other factors leading
to a gasket failure. Coupled with visual inspection for ten other features, we can normally determine why a gasket
has allegedly failed.
The following pages are dedicated to Gasket Fault Finding.
For your further guidance remidial actions are suggested.