Car is a 1988 740 Turbo with M46, 240k miles. The problem was that the OD would not disengage after being engaged for more than ~10 minutes. When the OD button is pushed, the OD light turns off but the OD does not disengage right away (after a while it will disengage on its own). For short trips, the OD engages/disengages with the button as it should. Per the FAQ and ODGuru's instructions, I removed the solenoid, disassembled, cleaned with electrical contact cleaner, replaced all the o-rings, reassembled. The symptoms are still exactly the same - disenages properly on short trips, will not disengage after ~10 or more minutes of being engaged.

What next???? Replace the entire solenoid? Is there a pressure relief valve in the OD somewhere?

Zack
1980 245DL M46 294k
1988 745T+ M46 240k