donch@teklabs.UUCP (08/26/83)
I've got a good one for anyone specifically familiar with BMW's. My 72 2002 with >100k miles, maybe 105k, has slow oil pressure buildup. With a cold engine, from the moment the engine catches to the first indication of oil pressure, I've timed 5 to 10 seconds. At first, I didn't believe the idiot light. Then a mechanical oil gauge added to the dash confirmed the timing. Besides, the engine noticeably loads down (and quiets down!!) at the same moment as pressure appears. Otherswise, the oil pressure runs within the specs stated i n the factory manual. I know this is doing nasty things to bearings, particularly o n the crank, so I've added colloidal graphite to my engine oil (Kendall 30 wt) to get a bit of "dry" lubrication protection until pressure builds. One possible clue is that the oil gauge is extremely noisy, rattling at a rate that is directly proportional to engine rpm. Putting my ear to the face of the gauge lets me hear quite a rattling sound, assuming there is a valid stethoscopic analog in play here. It sounds like the oil pump is putting out very powerful pulses as opposed to a fairly sustained pressure. Not knowing BMW oil pump design and construction, and getting precious little from the manual on specifics, I have some guesses. The main one is that there is a relief valve somewhere that allows the pump to lose its prime. Or that instead of a relief valve, there is a defect somewhere that is in effect a relief valve. I didn't notice this problem until after discovering and hopefully curing another. Namely, BMW rocker shafts are fully pressurized by the oil pump as they supply oil to the rockers. These shafts have plugs pressed into one end to seal them. The plugs can and do come out. Mine was forced out and into contact with the back face of the cam chain sprocket, giving it a lovely polish. Oil pressure was very bad--my first clue. After fixing that by virtue of a cold chisel and a sledge (yes, I almost threw up when a well respected local BMW mechanic told me that is the simple and effective cure), the oil pressure was back to spec. Since then the current problem arose. Any thoughts and suggestions are welcome. Between my wife's and my 2002s, I've some interesting problems in need of solutions that I'll post when time allows. Don Chitwood teklabs!donch Imaging Research Labs, Teklabs Tektronix, Inc. Beaverton, OR
emma@uw-june.UUCP (08/26/83)
My Toyota has also built up initial oil pressure very slowly, for as long as I have had it. It now has 93K miles and no apparent wear problems, so I don't worry about. I also don't touch the gas pedal until I get pressure! -Joe P.