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

If you are not sure what the problem is, do not run it.
1) Check your oil level. If very low, check for external oil leaks.
2) Borrow/rent/buy an manual oil pressure gauge " Remove thee oil pressure sending unit and connect the manual gauge on the engine block.
3) start the engine. If no pressure on the gauge....it looks bad (oil pump failure or worst). Stop everything.
4) If you have normal pressure on the manual pressure gauge, two possibilities
a) Faulty oil pressure sending unit
b) faulty dash gauge.
Good luck
jackd

I also meant to ask how difficult it is to replace the oil pump or oil pump chain?

Is there an online shop manual that shows the steps to replacing them?

Thanks,

Jerry

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

It sounds like you've run the engine a bit with no oil pressure, assuming the gauge is correct.

You may have a problem in the bearings now. We had a Dodge Caravan years ago. It had a Mitsubishi engine that broke the oil pump drive chain. It did in the main bearings, too.

Maybe you'll be luckier, though. I wouldn't run it any more until you figure out the problem, though.

__________________
2012 E350
2006 Callaway SC560

I am trying to remove the oil pan to get to the oil pump but have not been able to get the pan clear.

Can anyone tell me what the trick is to getting the oil pan out?

Thanks,

Jerry McColgan