190E 2.3-16v Oil Pump

[BenzMacX]

A while back a chain rail fell of and clogged up the oil intake for a good long while (the car was driven no where while this was going on). In the diagnosis of that I replaced the oil pressure gauge, the pressure relief valve at the exit among other things. I just tripped out to Indiana for school (Purdue University) and about 200-miles out my oil pressure started acting up. Before the trip my oil pressure was always at 3 above idle, i know that for a 16v it should be at 3 at idle as well (thats not critical, but the more robust oil pump of the 16v keeps it there). So I figured that the oil pump was damaged when the chain rail fell off and clogged up the intake. Now, however, I have some bigger problems. With a cold car the oil pressure will still hit 3 bar, but a warm engine at idle will go down to below 1bar and close to 0! I know .3 bar should be acceptable, but something is obviously broken and its getting worse so it needs to be fixed.

I think there could only be one of 2things wrong right now and I need some help. The oil pump could be worn out and needs to be replaced, or the other pressure relief valve is gone. Its probably the oil pump. I do not have my repair manual out here with me, but I will get one. I just would like to know what I am getting into and what is involved with replacing the oil pump. What needs to come off and how much of a pain in the ass is it?

Thanks,
Jim