BMW E30 M42 Oil Pressure issues

[robertlacayo]

Hello,
I need some help with my BMW E30 M42. I recently replaced both the upper and lower oil pans, including the gaskets, twice. The first time, I didn’t get a proper seal. I ended up using RTV and Loctite on the inner oil pan bolts. Now, when I start the car, everything seems fine until I drive for about 5-10 minutes. I notice the engine gets louder, and the oil light flickers when I stop, but goes off when I accelerate.

I’m doing some research to diagnose the issue. I plan to try using a heavier oil since I'm currently using 5W-30 full synthetic, and I’ll also perform an oil pressure test. From what I’ve read, the spec oil pressure should be around 18 psi. If the test fails with the heavier oil, I suspect it might be the oil pump. I've read that it is accessible from under the Engine. Can anyone 2nd that? or Provide a DIY? I haven't been able to find anything.

Any advice is appreciated!

[mike.bmw]

Was this an issue before sealing the upper and lower oil pans?

How much RTV did you use? If you used too much, some of the excess could have detached from the main bead and it might be blocking the pickup.

I believe the pickup is accessible by removing the lower pan, which doesn't require the subframe to be dropped.

[uturn]

Pickup is in the lower pan but oil path goes through upper pan and front cover. Oil pump is in the front cover and you'll have a blast getting to it!

[varg]

Put a gauge on it asap to see if it's just the sender or if the pressure is actually low.

M42's oil pickup tube bolts to the upper pan and goes through it to the rear timing case which holds the oil pump. If you were to use too much RTV and it went into the pump it would be discharged from the pump directly into the filter housing and should not make it past the filter nor cause low oil pressure unless it got jammed in the relief valve or damaged the pump (it's a gerotor pump, the outer gear could be cracked by a piece of debris between it and the rotor). As I recall, most M42 oil pressure issues are because of the thin part of the gasket between the pickup passage in the upper pan and the pump inlet in the timing case leaking air, often because of upper pan bolts falling out into the sump. It would take a lot to fall into the sump to block the pickup enough to cause low oil pressure imo. I'd pull the lower pan and smoke test the upper pan passage or see if you can get your hand up to the sealing surface between the upper pan and timing case and feel for air being blown out when you blow into the pickup tube (low pressure shop air or mouth). That would indicate an upper pan gasket issue. If you're unable to narrow it down to a leak in the pickup tube gasket or upper oil pan gasket I'd suspect the pump is damaged. I'm not even sure if a blown out chain tensioner piston will let enough oil out to cause a low oil pressure light. Low oil pressure is more of a typical M20 problem than M42, M42 problems are unseemly numbers of leaks, crank walk, and timing chain stuff.