View Single Post
Old 01-03-2002, 09:49 PM
psfred psfred is offline
Registered User
Join Date: Aug 2001
Location: Evansville, Indiana
Posts: 8,150
Nope, a cracked head will allow the 1500 psi combustion gasses to leak out into the cooling system any time the engine is running. Usually not enough pressure to force the coolant back in (a good thing, as the rods will all be bent if you try to start an engine with water in it!)

Evey compression/firing stroke will drive gas into the cooling system, the amount depending on the size of the crack or leak in the head gasket. Some cracks work the other way, slowly sucking coolant into the combustion chambers -- coolant dissapears without a detectable leak.

The cooling system should be almost completely de-pressurized until it get to operating temperature, and even then won't get to full pressure unless you have a large heat load, as in driving in traffic with the AC on. If you get substantial pressure below operating temp of within a few minutes this time of year, you have a combustion leak into the cooling system.

1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
Reply With Quote