Low oil pressure? Help!

[wmrfoster]

I have replaced the oil pump and dropped the oil pan to check the sump but can't find out what the heck is causing my recent low oil pressure problem! IT started early one morning and then went away. Came back the next day and went away. Then on the day I was taking it to my brother's service station to check it it got really bad and then went away long enough for me to drive to his shop. So far we have ripped apart the timing chain housing and replaced the oil pump even though the old pump was in tolerances. It now gets around 15 PSI and that's it but the oil light is now out but the engine runs badly and seems like the oil is not getting up into the head. Bottom of the engine seems fine with no obvious damage and there was no blockage in oil sump when we pulled the oil pan off!
The question is could this be related to the Oil pressure relief valve? We pulled it out and it seemed fine although it was scatched up pretty good. I wire wheeled it and reinstalled but how can you tell if this part is bad? We have NOT found any reason why I would be having oil pressure issues suddenly out of no where. Is there anyway to find blockages in the engine without ripping it apart again? Any suggestions would be greatly appreciated even though my Brother is a good mechanic he has no background in Beemers and he is as stumped as I am at this point!
Thanks!

[sheepdog]

Could be the relief valve, but also check the upper pan gasket as well as the gasket where the pickup meets the upper pan. Could be a failed gasket or maybe one shifted.

May also want to check the pickup screen itself, as it may be clogged with something.

[wmrfoster]

Well what happened is this the chain guide had cracked and broke into the Timing Chain housing and a metal piece big enough to entirely cover the sump opening had somehow worked it's way all the down into the pan. It was a flat piece that we didn't see right away until I completely cleaned out the bottom of the pan. So it was a good thing we pulled off the Timing chain housing first because I fixed that plus replaced the oil pump, relief valve, front seal while I had it apart. So after alot of work and effort at least it is fixed and I got to replace alot of parts in an older engine (199,980!) and I know I have some more time before a complete rebuild is necessary. I know alot of people do not like the M42 but that engine has been pretty good to me for the most part and has certainly given me my moneys worth so far!


So thanks for the responce but I have my baby back and she is running stronger than ever! :D

[sheepdog]

I know I have some more time before a complete rebuild is necessary. I know alot of people do not like the M42 but that engine has been pretty good to me for the most part and has certainly given me my moneys worth so far!

325 guys think it is low on power but seem to think it is bulletproof.
318 guys think it is bulletproof, but fine on power.

Truth is, it is not a bad motor, but not as bulletproof as many like to think. Until this site came along most people thought it was nearly bulletproof. they also thought the engine had no potential, now we know better.

Personally, discounting its weight (it is VERY light) it is nothing special. The weight is its strong point, it weights almost half of most other engines.