E39 Oil breather system

[Jez49]

I recently changed the cam cover gasket on my 530 and found the breather pipe that goes from the cam cover to somewhere under the inlet manifold was broken so I replaced that as well - nightmare job due to the inlet manifold restricting access.

I did all of the above because I occasionally smell oil fumes in the car coming in from the heater when it first starts up in the morning, particularly if its not had a good run for a while and has done lots of traffic work.

In terms of the oil breather system what is under the inlet manifold that could give problems and give off this smell? Ive raised the bonnet after driving to work and theres no evidence of an oil leak and no smell of oil vapour!

Thanks

Jez