Hi all,
I'm helping out my friend with his ~ '91 740 N/A car.

It's got a few problems:
Way too much Crankcase pressure. There's a lot of air that comes out of the oil filler hole when the cap is off. So far the seals are ok but the Oil pressure sender is leaking and we'll swap that out.

I already have a Oil Separator box to replace the old one which I would guess is plugged (the flame trap is fine...)

The real problem is that his coolant turns BLACK (not brown). About a month or two ago had had his coolant replaced/flushed by a shop (they were of the opinion that 'the only way that coolant can be black is if someone put oil in the coolant reservoir...' (doubt that) and for a while it seemed ok. now it's starting to turn black again...is the excess crankcase pressure somehow forcing oil into a coolant passage? The HG seems fine- the car runs well and has run on black coolant for a while (1+ year) with no real problems...except that it's black)

What might cause the coolant to do this? I read in my googling that degrading rubber hoses can do this, or adding dextron rather than old fashioned coolant...?

I'm worried that if we lower the crankcase pressure by restoring the PCV system, the pressure that is (possibly) forcing oil into the coolant will be gone and allow coolant to mix with the oil (the oil is fine- no milk shake), same with tranny fluid, although it's been a month since I checked it)- is this a valid concern? where can I look to attack this?

Sorry for the wordy post- thanks for any help!
Koos