Phantom oil leak

[tomTVR]

Heres an interesting one for you guys.

My BMW 740i has been dripping oil for a few weeks slowly getting worse and worst to the point where today it must have lost half a pint as is cooled after driving. I then topped it up with 3-4 litres of fresh stuff and went for a fairly long and fast drive. Pull up and the leak has practically stropped, only a couple of tint spots yet the level is nice and high.

Only other symptom is notice that wasnt there before is a high pressure whistling sound (like air escaping) that carry on long after the engine has stopped.

Only thing i could think of is possibly the oil is escaping somwhere else possibly into the coolant? Still strange that it would totally stop leaking from the bottom though.

Any ideas? Thoughts very much appreciated.

[BB-Q]

Take the oil filler cap off while the engine is warm and idling. The 740 should try and suck the cap back on- i.e. have negative crankcase pressure. If you've got positive pressure you've found your problem.

The other possibility might be a crack that opens/closes up as the engine warms. I've had that problem before and it took me ages to find it.

[Holst]

Check for oil or mayo in the rad to see if the oil has got into the water.

It might also be worth checking your vacume hozes for splits (of if one has fallen off) but this probably isnt it as you lost quite a bit of oil.

Do you have any idea where the oil came from?