vacuum pump rebuild question - Page 3 - PeachParts Mercedes-Benz Forum

Stevo · #31 03-06-2009, 05:00 PM

I also rebuilt one that couldn't get 'down' to the proper vacuum, I'll be interested in your out come.

Diesel911 · #32 03-06-2009, 11:33 PM

I would also double check the direction the valves inside were put in.

ichbineinekrous · #33 03-07-2009, 12:18 PM

I've got the two valves that go together both facing so that the raised part of the check valve is down, and the single valve opposite the two is the other way round, raised part up. By up and down of course I mean up being pointed away from the block. Stevo, I don't want to hear that! What did you end up doing? I've put out a request for a salvage vacuum pump but so far have only found one guy who's willing to sell it w/o the block. There aren't any pick and pulls to my knowledge around here.

Stevo · #34 03-07-2009, 02:35 PM

Quote:

Originally Posted by ichbineinekrous

Stevo, I don't want to hear that! What did you end up doing?

I pulled it and couldn't see what was wrong. I installed one of the older type, diaphragm type pumps, problem solved. I would like to be able to fix it for a spare if the "O" ring is the problem.

Diesel911 · #35 03-09-2009, 03:24 AM

Quote:

Originally Posted by ichbineinekrous

I've got the two valves that go together both facing so that the raised part of the check valve is down, and the single valve opposite the two is the other way round, raised part up. By up and down of course I mean up being pointed away from the block. Stevo, I don't want to hear that! What did you end up doing? I've put out a request for a salvage vacuum pump but so far have only found one guy who's willing to sell it w/o the block. There aren't any pick and pulls to my knowledge around here.

From looking in the FSM the 2 Valves (items #5 in the pic) next to each other both have the Pointed parts facing towards the Engine (if the VP was on the Engine) and 1 valve (item #2 in the pic) that goes up by the Check Valve has the Pointed part Facing towards the Radiator.

ichbineinekrous · #36 03-09-2009, 11:05 AM

yes exactly, thanks for the confirmation. I've swapped the old gaskets around the check valves back in, and will be re-installing today, possibly will also put the old fiber ring and piston o-ring back as well. I'll post the results, but I'm not holding my breath.

ichbineinekrous · #37 03-11-2009, 09:06 PM

put it in again, with the old gaskets around the check valves, new mickey mouse o-ring, and the old piston o-ring and fiber ring. pump seemed to be making vacuum as I pushed on the base of the piston, but after install I'm still only getting 5 psi which takes a few seconds to attain at idle, and 10-13 if I rev the engine to 3000 rpm. I'm completely knackered.

ichbineinekrous · #38 03-31-2009, 04:26 PM

I give up. Now looking for a used vacuum pump, or the location of a pick and pull yard somewhere between Raleigh, NC and Central PA. Don't have the money for a new one and all the indys in Raleigh I've talked to won't touch it.

mash · #39 03-31-2009, 05:35 PM

Dear ichbineinekrous,
I'm sorry to hear about your vacuum gremlins. I went the same route as you; rebuild kit, check valve replacement until I finally found the leak. It was the Brake Master Cylinder to Brake Booster SEAL or O-ring!!! It has square edges unlike the circular norm. The master cylinder is attached to the booster by two 10mm studs. Once separated carefully clean the mating surfaces, install new seal and tighten to no more than 7 FtIbs and try not to push or lean on the BMC once installed to avoid future leaks. I have a vacuum gauge installed in my glove box so I can keep on eye on changes. The gauge reads as hi as 26 at 65MPH and drops to 22 in heavy stop and go traffic. Also interesting to note when I go up to an elevation of approx. 10,000 feet in the local mountains the gauge won't go higher than 20 because of the thin air. Anyway, it sounds like you're working very carefully so with all you've done to your vacuum pump I would bet that it is not your leak source. Also the hose between the checkvalve and Brake Booster has metal to metal sealing. Sometimes after much opening and closing too tightly the sealing surfaces lose their ability to seal no matter how much torque you apply. Another thing is a possible crack in that same hose at the t-junction where vacuum is drawn off for the rest of the car's systems. If I had a leak now I would start by blocking off that t-junction feed to the rest of the car so I could isolate the problem and go from there. I also know there are smoke machines you can use to find vacuum leaks which really helps when the leak is in the car where you can't access plastic and rubber hoses easily. Smoke machines can be rented. Anyway good luck, I'll keep an eye out for you reply.

ichbineinekrous · #40 03-31-2009, 09:43 PM

I've done a fairly complete job of narrowing the problem down to the vacuum pump. Tested the level of vacuum with the brake booster line plugged and disconnected from the brake booster. Thanks for the ideas.