Posted by Jared in S-W on September 03, 2004 at 21:36:25 from from 198.81.26.40
In Reply to: Bad Oil Problem posted by Thomas R. on September 03, 2004 at 18:44:31:
Ive been a Lube Technician for 3 years now and this is usually a problem you only encounter when you change the oil and filter i.e. engine knocks lightly until the oil filter housing fills completley with oil and then distributes throughout the motor, the main and rod bearings and then the valve train, and then of course the knocking stops. I aint no beemer mechanic, but since the oil filter canister retains oil when the engine is shut off I would definitely say you have a oil pump problem (the oil may be draining from the pump back into the engine) Im not sure if these engines have an anti drain back valve but if they did that is what I would say is causing noise on startup, HOWEVER it does not explain the drop in oil pressure once the oil has warmed.
One other thing to consider is that worn rod or main bearings will have the same symptoms associated with your description i.e. no oil pressure accompanied with knocking or rattling and then low oil pressure once the oil has warmed to operating temperature. I myself owned a 84 toyota celica that I knew had a rod knock when I bought it and it eventually got so bad that I was running straight 80/W90 in the motor to combat this, as you can imagine it didnt last forever but it showed the same symptoms that you are describing.