Turned out to be the sending unit. I hooked up a mechanical gage using a banjo fitting from a 123 diesel. Never went below 1.2 bar at idle and over 3 bar at around 2500 Rpm. No noise from the lifters. All of this may have been brought on from not changing the oil for over a year - we don't drive it much. So, I have 1 more thing to be thankful for on Thanksgiving - I don't have to pull the filter housing or the pan! Craig

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90 300SL Pearl Gray
92 300CE Smoke Silver