I have been chasing a blue / grey smoke problem in my w115 1975 240D for a few months now on the vintage forum(this thread), thought maybe some fresh eyes here might help. I only get smoke when pulling away after the car has sat at idle like a stoplight, but it’s enough to see it buffet off the car behind me. Once moving the smoke clears or perhaps I can’t see it anymore. The engine pulls very strong although it is the only 240D I have driven. Compression is above 380psi in all cylinders and I believe at least part of the motor was recently rebuilt.

Here is what I have ALREADY tried:

1. Cam chain timing is correct, zero stretch.
2. IP timing is on.
3. Valves are in adjustment.
4. Valve stem seals have been replaced.
5. Vacuum pump is not leaking oil
6. Oil bath filter is clean and not over filled.
7. IP diaphragm has been replaced.
8. IP oil level is correct.
9. Injectors – recent tips, pop tested and calibrated.
10. Popet cam housing on back of IP was rebuilt and IP holds vacuum per FSM (See post 30 on the above linked thread for details, this is a pneumatically governed car unlike the w123’s)
11. Fuel has been replaced, both filters replaced.
12. Fuel additive used.
13. 1 QT ATF run through in last tank.
14. Crank case temporarily vented to atmosphere, no improvement.
15. No oil in coolant, level stay constant.

I considered stuck rings, but would I have great compression and still have stuck rings? The valve guides are the only other thing I can think of but I don’t relish the idea of having the head rebuilt.

Any thoughts?

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1972 280SE 4.5