Folks, about every other month, for a few days at a time, I will lose most of my vacuum, causing the brakes to be very hard, and causing me to sometimes have to open the hood to turn off the engine. I have sealed off the driver's compartment from the vacuum system, so it is not a leak in the doors. I have been told that there are some valves in the vacuum pump that are not working correctly, and that is causing the problem. My question is this:
How much of a hassle is it to rebuild or replace the vacuum pump? It is my understanding that I will need to remove the radiator, and that perhaps a kit exists that would allow me to rebuild the vacuum pump. Does anyone else have any experience with this, and is it a relatively easy and straightforward task? Thanks so much in advance!

The pump itself is probably fine. There is a check valve in the nipple where the hard line attaches to the pump. The check valve tends to break. When that happens, the loose components intermittently block air flow into the vacuum pump.

You can remove the nipple while the pump is still in place. I would suggest that be your first step. You will probably find that the check valve components have dropped into the pump inlet.

I concur, tangofox told me that and despite my skepticism, was quite correct. Not sure I could have extracted the little valve parts but they are probably blocking the intake valve and you might be able to fish them out. I rebuilt mine because I had a kit on hand. It wasn't difficult, but you have to build a little stand and follow the DYI instructions.

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1983 CD
1958 Studebaker Packard (being resuscitated)

Just sent you an email with links to some pics.

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1983 CD
1958 Studebaker Packard (being resuscitated)

You don't say which car, but the intermittent nature of it tells me the odds are you just need to buy this part:

http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=26W03483526W034VKV&year=1983&make=MB&model=300-DT-001&category=All&part=Vacuum+Pump+Check+Valve

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)

Pselaphid and all others:
Thanks so much for your advice and replies!

Do these check valves just thread into the body of the vacuum pump, and thus theoretically I could loosen the vacuum line, then unbolt the check valve and replace it without messing with the vacuum pump?

The pictures that Pselaphid sent me make the rebuild job look a little daunting! Thanks again for your help

If the pump is of the piston variety, the answer is "yes" on all counts.

So that we don't make invalid assumptions, could you tell us what car we are dealing with?

Yes, you can replace the valve w/o removing the pump.

Need to know the model and year. Early 123 pumps are rebuildable on the engine by just removing fan blade and shroud. Takes about an hour. Later models are different. I'd replace the diapragm if I was going to disassemble it far enough to replace the check valves.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

I rebuilt mine. I didn't need the test stand. I didn't have any problems before, I just removed the pump to get to the timing chain and other parts. The person who sold me this car had problems with his vac pump. He had to replace the check valve. I swap him mine for one he had on order. So, I'd pull the check valve and see if there is any damage to it. There was oil back to my brake booster. It was replaced. As I remember, I took a scocket and placed it underneathe the pump on the bearing and pushed down. Both during dissasembly and reassembly.
Tom

Folks, thanks again for all your help and advice. I don't think I'm up to messing with the timing chain - Does anyone know how much a rebuilt vacuum pump might cost?
By the way, this is for a 1983 300D
Thanks so much again!

Again, can't answer without year and model. The 617 engine had two different vacuum pumps, an early and late. Early one is a simple rebuild, later requires more work.
If you can't give the year and model, does the pump have a line going over to the air filter?

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

I'm sorry, I thought I had mentioned that it is a 1983 300D Turbo Diesel.

It's the later pump which is more difficult to rebuild.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

First, I only said I rebuilt mine while i had it off for the timing chain. You actually don't have to take off the vacum pump to replace the timing chain though. I wanted to replace the bottom two guides for the timing chain. So you don't have to replace your timing chain.
Anyways, here's a link:
http://diymbrepair.com/easley/Rebuild_vac_pump.htm
Might bookmark it. I didn't built the fixture. I placed a block of steel or a socket underneathe and pressed down. I'd check the bearing, if its damaged (ie bearing balls not equally spaced or look damaged) then but a new pump. That assembly is like $175 or more. Add the rebuild kit ($50 I think) and the check valve ($40 or so). I think a new pump with the new style bearing is $250-$300. I'd look at the check valve first, then the hose from the brake booster to it.
Tom