Mystery oil leak

[kanemack]

Hi everyone! S I noticed a pretty major leak coming from around the oil pan area. I Know the oil pan seeps a little, but the amount of work to replace it means it will wait until there's time to replace. My second thought was it looked like the oil level sensor was leaking, but after cleaning up the sensor, it doesn't look like it's leaking(running or just sitting there).

Then I realized that it only seems to leak when the oil level is where it should be, otherwise it gets to the bottom hatch mark on the dipstick, and doesn't seem to leak anymore. Any ideas or has this happened to you?

Oil engine light only comes on once in a while. Seems only when driving(Haven't seen it on when sitting still).
The car has 250k on the chassis, and the top end was rebuilt about 10k ago

I'll get the drivers side of the engine bay taken apart so i have more access to that side to see if it's a hose. I'll be changing all the coolant/heater hose(s) as I already purchased a kit from FCPEuro($80 great kit!).


Also it's a 1995 525i touring

I'll report back with progress, and any ideas will help greatly.

Have a nice day!

[jint45]

That would normally be front or rear main seal if the level affects the leak

[kanemack]

Thanks for that...I guess i was hoping for any easier fix. So out comes the engine hoist. I think i can take off the motor mount bolts and lift the engine enough to sneak the oil pan out. If this has been tried, and failed, please let me know. In that case I'll pull the engine out completely just a couple more hours of work. If that's the case, I'm going to detail the engine bay completely.

As always all the help I find is greatly appreciated!

[kanemack]

Looked at part, Though it was similar to a China rail seal but on the bottom, in like an ls. Looks like engine has to come out for the rear.

[fo3]

The dipstick tube has an o ring on the bottom of it that commonly leaks. It's nearish to the oil float (which was your first suspect), so it could be that. Just undo the clamp bolts that attach it to the inlet manifold support bracket and pull the tube out, replace o ring.
On mine (1990 m50NV) it's part# 11431287541 , a 14.5mm x 3mm o-ring, but double check on yours.

If it's not that it's going to be all the other places where they leak (sump gasket, front timing cover gaskets, oil filter housing gasket etc etc. ) I've fixed all mine except the front crankshaft seal

E: If the rear was leaking you would only see oil dripping from the bellhousing weep hole (and oil traces going from there backwards onto the trans). So it's unlikely if that isn't the case and you instead see oil near the oil float sensor area.

[kanemack]

It was all over the bottom of the pan. It's going to be warmer tomorrow so I'm going to be diving in...I'm hoping for the best, but prepared for the worst. I ordered new seals in case, because I don't want to wait for shipping while I forget where bolts go.

Also, I saw that it might be easier to drop the trans if it is the rear seal. I have an old school mechanic from Poland helping me figure it out. Wish me luck!

Thanks for all the help!