I am concerned about the oil pressure reading on my 1993 300E 2.8, 146K miles. At startup, when cold, the pressure only reaches the 1.5 range, slowly falling to zero as the engine temperature reaches the 80 degree celsius mark it normally operates at. I have changed the oil and put in a Bosch filter, (which was also the brand of the old filter), but the problem persists. I do not hear valves or lifters rattling and I can see oil when I remove the oil filler cap, so I believe there is a decent flow of oil.

Is this symptomatic of a faulty oil sending unit? If so, how the heck do I replace it? I can see it with a flashlight just below the oil filter, but I don't see a way to get to it as it so close to the firewall area, nor do I see how it would be removed if i could get in there. My searches have revealed similar problems, but no one has described how to actually replce the sender, if that is the problem at all.

I'd appreciate any suggestions on what steps I might take to get to the source of this problem.