My friend the MB mechanic has a problem car in his shop he cannot diagnose, so he asked me to pass this on in case someone else has run into the same problem.

Car is a 1994 420E, always properly serviced (mostly by him, I think) with 80,000 miles.

Symptom is low oil pressure at idle hot. Pressure comes up pretty fast with increasing rpm. No obvious reason (ie good oil, engine runs well, no leaks, no noise from lifters).

This is what he has done/checked so far:

Oil tubes on cams (no leaks -- but what a pain to get to!).

Oil sending unit is good (oil pressure is low on an external gauge, too).

Not a bad cam tower or other internal leak on the upper end.

He was going to pull the oil pressure relief valve on Thursday to check it.

He is concerned that there is a main bearing with excessive clearance that isn't making any noise.

Issue started recently.

Any thoughts out there? He's covered everything I can think of, he's stumped, and he's been working on MBs since 1959!

Peter

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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!