Vacuum pump issue on 300TD? Need help

[pinpoint]

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

[junqueyardjim]

It is very easy to check if your pump is faulty if you have a vacuum guage. You can't feel much vacuum if you put your finger at the end of the big vacuum line, you can feel a "little". OK, you do have a vacuum gauge. So disconnect the big line from the vacuum brake booster. Clean and easy to do. Hook your gauge up to one of the small outlets, usually there are two of them. Use either one, and block off the other one. Start the engine, hold your finger over the open end on the big line. Instantly you should have between 15 and 22 inches of vacuum. Weather and altitude can change it a little, but with that hook up you should show a good vacuum. If you don't the pump is not doing its job, and rebuilt pumps cost about as much as a new pump, now selling for a little less then $400.00. I do have a good used one for sale.

[pinpoint]

Thank you very much for your input. I had done the steps you indicated previously and just did them again to be sure. At idle, I am getting no reading, and when I rev, I can get like 5lbs. I guess this,might mean the pump is working but not at its given capacity if you,say I should be seeing >15 lbs, huh?

Also I would you know if lack of vacuum affect the turbo operation at all? (I don't believe the turbo has worked properly for some time, but the car is clean and runs great even w/o)

[BWhitmore]

Your vacuum pump is faulty. Replace the vacuum pump with a new pump (including new check valve) and you will see a lot of things return to normal including engine shut off, power brake booster, door locks, AC operation, etc. Vacuum pumps have been know to explode internally taking out major engine parts with it (timing chain, camshaft, camshaft towers, etc.).

[pinpoint]

Thanks. There are a few rebuild kits around and some complete pumps, so even though the cost is making my eyes water, I will Probably go with the latter. It would be nice to get all the normal functionality back.

[Diesel911]

If you have plenty of time simply remove the Vacuum Pump and take it apart and see if you can find something specifically wrong with it.