Annoying oil leak..help diagnose please

[Rajvosa]

Hi all
bought a 2004 M3 (my 10th one) and quickly worked out CPV had a leak. Replaced with another valve with good o ring I had laying around. Anyways couple days of driving and oil is pooling again in the spot where box and engine meet.

CPV looks totally dry from underneath. (Rear main seal was done maybe 10k kms ago..). Anything that could leak above the passenger side engine mount (driver side for us in Australia)? Valve cover gasket also done and looks dry…

I’ve left underbody shield off just to keep a better eye but any advice appreciated!

Thanks all!

[AWE46M3]

haha - jk. With this platform and the cars being 20+ years old, it could be anywhere. I'd clean everything up as thoroughly as possible and add the UV dye to your engine oil to see if you can trace it to the source.

I've got Anri going through my car right now and when he was doing my front main seal he found a stud that had vibrated loose over time behind the harmonic balancer that was leaking quite a bit.

Leaks I've found in my ownership so far were...
oil filter housing gaskett
oil return line the top of the engine to the oil pan
vanos oil pressure line
front main seal
rear main seal
cpv
oil pan gasket (this one is a massive PITA)
oil pan strainer gasket
valve cover gasket
vanos gasket

I'm sure I'll be adding more to this list...

Good luck

[oceansize]

Exhaust camshaft sensor o-ring.

[sapote]

Feel around the back of the head for any oil leaking from the big hex plugs or the so-called freeze-plugs that often see on the engine block.

[PSUEng]

Hi all
Replaced with another valve with good o ring I had laying around. !

Thanks all!

Well, not sure what that means but I'd either 1] get a viton replacement (some members here offer these) or 2] replace with OE (but will leak ultimately...choice [1] is better).

As stated, 20+yrs old, get ready to find leaks. Good luck.

[BL92]

Is it gearbox oil? could be like mine and be the Input shaft seal ?

[Rajvosa]

Update:

have spent some more time trying to diagnose this leak.

it’s not the vanos accumulator. It’s not the hex bolts behind the head. Not crank sensor.

Oil pan gasket was done about 3.5 years ago and car has only done about 7500 miles since but I’ve taken this pic. Looks like oil coming from above the bolt hole…

[Rajvosa]

Mechanic had a look at it. Applied some tread sealant on few oil pan bolts. Sorted some of leak but he reckons a small leak coming from front timing cover. I’ll monitor how it’s going over next couple drives

[George Hill]

Put some leak detection dye in it.