Greetings. Had an odd combination of things happen while working on my '85 300TD. After adding some R134 to the a/c this past weekend, I experienced the dreaded non-shutoff problem. Then my son (who's inheriting the car from me) complained about a hard brake pedal and difficulty stopping. Figured I knocked a vacuum line out, right? Not so. I double checked and made sure all of the lines were connected (w/new rubber ends).

Last night I put vacuum gauge on both of the nipples on the (fairly new) brake booster vac line, and got no vacuum. Today I decided to unplug the brake booster line at the booster and then feel for vacuum. When I raise the rpm I can feel a little vacuum. When I plug the booster end with my finger, I now am pulling only about 5 lbs at the nipples on the booster line (with the other nipple blocked. This is obviously not enough to shut off the engine.

My internet research has indicated that it could be a faulty vacuum pump, or possibly a valve on the vac pump. I'm usually skeptical about automatically replacing expensive parts without isolating the problem. (That's what the stealerships do, right??)

Anyhow, I'm hoping that someone on this forum might have some additional insight or troubleshooting suggestions before I pull all my hair out. I guess the only thing I have not done is to try to hook a vacuum gauge directly to the vac pump to see if I can maybe get a reading.

Any advice is greatly appreciated. Thank you!

Jeff