Vacuum pump rebuild?
 

So I have been reading up on vac pump failures and preemptive rebuilds and was wondering about whether it is necessary if vacuum pressure is ok and there are no leaks or noises from the pump.
Does the pump slowly fail with warning signs beforehand or does it just grenade suddenly without warning?
I am not averse to rebuild if it truly is an expected problem.

Loss of Vacuum
 

'May your first clue.(Unless you regularly stick an "S"scope around in the engine
compartment.)[I can never hear anything over the natural Diesel noise of the
engine whether it's a Pre-Chamber or Direct]
EDIT: We'll go with Cervan's suggestion...a New Pump!

most rebuild kits are worthless since they dont have the actual bearing that goes out. Buy the updated vacuum pump that meyle sells.

I have 'scoped the pumps and other than minimal mechanical sounds I can hear nothing unusual; but I am a novice and not experienced in the sound a failing v-pump makes.
What would i be hearing if it is going bad?

Some make a noise, some stop pumping, some just go out with no sign. And destroys the engine.

Last year I ask a question as to what people thought caused their timing chain failure and may felt it was the Vacuum Pump.
Quite a few said that there was a unusual/ticking noise before the failure. And, what I thought was odd is several people said it failed right after they started the engine and started moving or shortly after they started moving.
What I got from the responses was that if your car starts making an abnormal noise; open the hood and see if you can find out where the noise is coming from. If it appears to coming from the area you are better of not driving the car until you know for sure.
After reading the responses I pulled my Vacuum Pump of and inspected the bearing, arms and other parts. I decided that if I can get myself motivated to do it I would like to pull it off in a year or so and inspect it again.

the VP constantly gets lubricated by engine oil. I found this out one time when I had it out and accidentally started the car. Oil squirts right into the gears.

The two bearings in the rocker mechanism are standard No. "626" (19mmØ x 6 x 6), deep groove journal bearings, available from any specialist bearing store, ± $5. Buy a reputable brand and do NOT use bearings that have dust covers even if they have been removed! A simple job to replace - press out the 6mmØ pin thro' the bearings and cam roller. Take care not to load the ball races when installing the new ones!!! Should last another 20 years.;)

I rebuilt the vacuum pump for our diesel and have great results. The symptoms came on gradually in our case, first with a slow shut down, then slower door locks. I waited until it affected the brake booster, which was way too late.

During the rebuild it was evident the problem was a torn diaphragm that probably started small and manifested itself greater as time passed. The rebuild kit was an M-B kit that addressed all the removable parts. In our case the bearing was not an issue.

Jim W.

I was wondering if the vacuum pump has anything to do with the way the transmission shifts/engages.

Do a search. If I remember my history right, you'll find that most all tranny shift discussions in here will talk about vacuum issues as the culprit.

The very first thing you need to verify when you're having transmission shifting issues is that you're getting proper vacuum from the pump. Should be something like 22 inches on a W123. So you'll need to get a vacuum gauge. I spent ~$30 for my mityvac and IMO it's worth it...also handy for doing fluid changes.

There's an article I used, I think it's on dieselgiant, that tells you several basic steps to go through to have your trans adjusted properly.

Yes, the vacuum affects the shifting. After our rebuild the shifting was like I remembered it should be.

I also recommend beginning your vacuum checking with a vacuum tester. First disconnect the vacuum line at the brake booster, then plug any or all lines between the brake booster and vacuum pump and check the main vacuum line with the tester. It should hold in the neighborhood of 20 inches for more than ten minutes. If it does it indicates the pump is OK, and, if you have vacuum problems, it is then a matter of isolating the source of the leak.

Jim W.

Good info, thank you. His, I believe, is the newer style piston pump. Do you know if the bearing size is the same for the earlier diaphragm pumps?

Yes, the bearings and roller on the diaphram and piston pumps are exactly the same. The rocker is also identical and interchangeable on both types. The bearings invariably fail due to the cages wearing thin and falling apart releasing the balls. Consequently it is impossible to determine thier condition by inspection looking for play. This is a job that anyone running the original pump should consider doing without delay.