I have a 1991 300E with a 2.6 engine with 235,000 miles on it. Until recently, it ran just fine (still does) but last Friday I noticed the oil pressure had dropped to zero indicated.

When I remove the oil cap I can see some oil flowing during idle but when I rev the engine up the oil flow stops and I hear a chain rattling at the front of the engine.

I don't know if I have an oil pump failure, oil pump chain failure, sending unit failure or what but it seems (since I do not see oil flowing when I rev the engine) that the problem is unlikely to be the sending unit.

How can I determine the correct problem?

Last week (before the problem started) when I would start the engine it would show 3 bars and after warming up it would show 1 - 1.5 bars at idle. At freeway speeds it would show 2 - 2.5 bars.

The fact that the oil pressure occurred suddenly makes me think the problem is not in the bearings.

I am new to this forum (or any auto forum) but I have done a lot of auto work.

I would appreciate any help with this (I searched the archives but have not found a similar situation).

Since the car is undriveable I would appreciate a quick response if possible (including how I can determine if the car can be driven without damage).

Thank you,

Jerry McColgan
Austin, Arkansas