Mercedes-Benz 603 Service Manual page 31

10 Fill cylinder with compressed air and read off
any pressure loss on tester.
11 If pressure is lost, determine cause; check
by listening whether pressure is exhausted
through cylinder head gasket, intake manifold,
exhaust, oil filler cap or prechambers of adjacent
cylinder(s) and check for formation of air bubbles
in coolant in coolant expansion tank.
Note
If pressure loss and air loss through the oil filler
cap are present , the possible causes can be
limited by spraying engine oil on the piston
crown of the cylinder being tested. The oil seals
the gap between the piston and cylinder. If
pressure loss is no longer present for a short
time, the cause is in all probability the piston,
piston rings or cylinder running surface.
The position of the piston ring gaps can result in
incorrect determination of the cause. If it is
suspected that the pressure loss results from the
piston ring gaps being positioned directly above
one another, completely reassemble engine and
repeat test after operating engine for a short
time.
01.10 - 01514
EXIT