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  #1  
Old 11-16-2004, 04:50 PM
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Vacuum Pump Failure

My 240D has the following symptoms (as of this morning): Won't Shutoff, Brakes hard, locks don't work too well. I checked for gross leaks and found none. Disconnected the main line and hooked the mity vac up to the main vacuum line off the vacuum pump with no users, and I get 5" of Hg vacuum at idle and a max of 10" at high throttle. My thinking was the vacuum pump had failed, but it is obvious that it has not completely failed. It certainly won't pull 20" of vacuum, as most of the troubleshooting posts seem to indicate it should. I never did see anywhere where it was stated what the performance should be. My expectation was a vacuum pump would fail completely, not partially.

Can anyone help me out? Is my vacuum pump the problem, or should I continue the search for leaks.

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  #2  
Old 11-16-2004, 05:43 PM
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Your vacuum pump is the problem. It should easily pull much more than that.
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  #3  
Old 11-16-2004, 06:01 PM
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yes. Leaking diaphragm, it should pull down about 28 in
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  #4  
Old 11-16-2004, 06:23 PM
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If you are lucky, than your problem may be a plugged orifice in the vacuum pump. I had the exact same symptoms on my '83 300Sd, and that's what it was.

At the Vacuum pump end, remove the large vacuum hose that runs from the pump to the Power Break Booster. Look closely at the little orifice that's there and see if its plugged. If so, remove the blockage. If not, keep on troubleshooting


Phil
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  #5  
Old 11-16-2004, 08:28 PM
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franklyspeaking

There are little check valves in there, I would give them a shot of brake cleaner. Mine were gummed up and the diaphram was fine. Worth a shot before you spring for the rebuild kit.
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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
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  #6  
Old 11-16-2004, 10:46 PM
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i tried to rebuild mine, and it failed right away. the original problem seemed to be gummed up values. that brake cleaner idea sounds great, wish i had seen this last year when my went...
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  #7  
Old 11-16-2004, 11:42 PM
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Thanks for all the replies....this helps but....

Pberku - I do not see the orifice you are referring to. I removed the tube going to the brake booster to check the vacuum pump performance. I saw only an empty pipe that I stuck the mighty vac hose into.

Stevo - in order to spray in the brake cleaner, would I have to remove the pump? Or can I spray into the intake and expect it to be sucked thru the check valves?

One other comment about vacuum pumps on 240D's. There are evidently two styles. The early style has a diaphram, however, it appears the later ones (like mine) do not. The rebuild kit does not show a diaphram - only some o-rings and some small metal parts - probably check valves? So is this some type of rotating dual lobed pump that only needs o-rings and check valves replaced?
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  #8  
Old 11-17-2004, 12:02 AM
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We are describing the same thing, but in different terms. I referred to it as an orifice and you are referring to it as an empty tube. In any event, in my case, that tube (orifice) was totally blocked. When I drove the car to my mechanic and explained him the problem that I was having (Exact same symptoms as yours) he knew exactly what the problem was, and described it to me even before he removed the vacuum hose. He was right. The passageway (orifice/tube) was totally blocked at the point where the main vacuum hose connects to the vacuum pump.


Phil
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  #9  
Old 11-27-2004, 06:46 PM
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For the record, I rebuilt the vacuum pump with the help of the DIY pages. I stripped out one 5mm bolt and dremelled it off (replaced with a 6mm hex screw purchased from Lowes). The pump internals looked good, but one of the valves was broken into 3 pieces. I guess this is what was preventing it from pulling a good vacuum. Everything works normally now.

I hope I don't have to take that fan off again for awhile. I had just changed the water pump about a month ago...and now the vacuum pump problem. Hopefully, I can make it until spring now with no major maintenance.
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Last edited by franklyspeaking; 11-27-2004 at 07:49 PM.
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  #10  
Old 11-28-2004, 10:45 AM
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Good show, then your back on the road. Sorry I missed your previous post. If the valve is "gummed" up it can sometimes be freed up by spraying brake cleaner in the "intake". This was in the older style pump and I assume the same would work on the newer style. So I guess new valves were included in the kit? I remember they were kinda spendy purchased separately.
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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
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"Lifes too short to drive a boring car"
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  #11  
Old 11-28-2004, 10:52 AM
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Valves were in good shape, however, as stated one was broken. I actually drove it up until Friday, when I took it down for repair. I'm a pretty slow mechanic, and so did not complete until yesterday afternoon. I did not road test, as yet. The whole kit is pretty pricey, if you ask me....for what you get. 3 or 4 O-rings and 3 valves = $70....ouch!!!!
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  #12  
Old 11-28-2004, 08:13 PM
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"The whole kit is pretty pricey"

Seems I payed $35.00 for a brake cyl check valve (just one) and they are not much different. Cant remember what I payed for the pump ones. A person could go into rebuilding check valves Ive messed with trying to rejuvenate them with little success.
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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"
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  #13  
Old 11-29-2004, 05:50 PM
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Though I previously posted a problem with my car not shutting off, I'll join in on this one. My car's locks will not work as well. I never thought about possibly the vaccuum pump since the transmission is shifting normally and the brakes are fine. Until I get a hold of a mighty vac tester, is there another route to take in troubleshooting a leak. Also, where do I began, at the pump?
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  #14  
Old 11-29-2004, 06:24 PM
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Testing the pump is an easy job...you do need a vacuum gage or a mighty vac, however. You just disconnect the main line from the pump and hookup a vacuum gage to the pipe. That way there are no users that may have leaks to worry with. The best place on my car was where the black hose from the brake booster connects to a short piece of tubing near the spin on fuel filter. I used some of the many hoses and nozzles supplied with the mighty vac to make this connection. I held it in the pipe with my left hand and revved the engine with my right.

When I tested mine, I got a maximum vacuum of 10" of Hg, which was way too low. When running down the highway the brakes functioned pretty well and the locks worked also, however, nothing worked while idling....especially after a cold start. My problem was a failed check valve in the pump. The rebuild kit contained new valves and so I am back in business.

Good luck!
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  #15  
Old 11-30-2004, 12:37 PM
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rebuild kit

There are not alot of parts in the vacuum rebuild kits from fastlane. Is that all you really need to rebuild the pump? There just seems to be some o-rings and some other pieces for $70.

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