82 240D Crankcase pressure at high RPMs

[yogarda]

Hello friends,

As many of you know, the gearing on a 240D with a 4-spd stick causes the engine RPMs to kinda soar at today's highway speeds of 65+ mph.

My trusty 240D has 283K miles, has been with me through 80K of them, and has had a front main leak that mostly only rears its head when driving over about 67 mph. I have been hypothesizing that the crankcase pressure got high enough at those RPMs to make weak old seals start to lose strength. This is not a smokey engine and has always been a strong starter even below zero. No noticeable smoke at startup or idle, and just the "normal" amount in people's headlights through the rearview at night. Oil pressure good and never overheating. Bosio injectors with 15K mi on them. Oil usage is not terrible like some other posts but generally occurs only when driving over that 67 mph trigger, at which I thought all the oil loss was leaked. The car does leave behind a little breadcrumb trail of oil drips after a highway drive. Never a WVO car or anything like that. 15W-50 in summer, Mobil1 10W-30 in winter (per service manual viscosities over varying temps).

Last night I was taking the car down to a detailer's with my girlfriend following, and she called me to say that there was a notable amount of white-ish smoke pouring out the tailpipe as soon as the car hit 65 mph. We switched cars and sure enough, intermittent "puffs" of white-blue smoke as soon as we hit 65. Not a constant stream, mind you, and I could smell "diesel engine" as I followed.

So my problem is more simply phrased: My car notably leaks oil and seems to burn oil but only when driven at high RPMs.

All that brings me to my questions. I've read about sticky oil rings, bad compression rings, and lots of other issues before posting this new thread. Does my problem sound like one of these kinds of rings? Is there any breather that should be venting the crank pressure that could be clogged? (There is oily crank pressure coming out from the oil spin-down back into the intake manifold, so that's not plugged but might be restricted.) Any other thoughts? Do I need a rebuild? I have taken such good care of this engine, never put a load on it before it warmed up, and was under the impression I should get at least 300K miles before needing a rebuild.

Sorry for the verbosity but I wanted you all to get a handle on many of the details without having to ask later.

Thanks guys for your time and thought.

Garrison