1990 240 B230F LH3.1 M47 333,000 miles

I've had a 5-bar oil pressure (OP) gauge in the car for close to a year. It has always hovered around 1 bar at idle, and gone up ~10 psi per 1000 RPMs. I didn't realize this was actually relatively low, although not dangerously.

Recently, on a very hot day, the oil got hot enough (210F according to the gauge) to trigger the OP light in the dash at idle. Not a flicker - as soon as the idle settles to ~750 RPM, with the oil at >200F, the OP light turns on solid. It does this everyday after a 20-30 minute drive now. The light DOES NOT turn on at higher RPMs.

OP test with a mechanical gauge**, oil at ~150F, showed:

~7 psi 750 RPM (idle)
~20 psi 1500 RPM
~30 psi 2000 RPM
~35 psi 2500 RPM

Obviously low! I replaced the oil pump o-rings 3 years/50k miles ago, so I am thinking it is the actual oil pump.

Anyway, I ordered the parts needed to do that job, and I'll do it ASAP. But, does anyone have any thoughts on the issue? I see a lot of talk about a flickering OP light (usually o-rings), and a few posts on worn oil pump relief springs (doesn't explain the low idle pressure). I am guessing the oil pump is worn - and I will be checking it when I pull it out.

As always, any help/suggestions/thoughts are greatly appreciated.


**The OP port on the front of the block is a PITA - I would never use that again. Recommend pulling the OP sensor and checking the pressure there.