Hi all,

My 1987 300D developed a strange problem suddenly. The cooling system remains under high pressure even when stone cold (left overnight). Yes, I have replaced the radiator cap. The car has never done this in the previous 4+ years I've owned it. The only way I can think of abnormal pressure in the cooling system would be from exhaust gas entering. How do I test if this is happening? The coolant looks clean and smells fine (to me.) There is no oil in the coolant or vice-versa. I suspect either the head gasket or a crack in the head (shudder.) I'm at a loss here... Help!


Dave M.
Sacramento, CA
1987 300D - 228kmi (weird cooling system problem)
1987 300D - 234kmi
1984 300D - 205kmi