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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1976 240D
1987 560SL
2007 E320 Bluetec
1998 C280 (now son’s car)
1982 240D Manual - Sold

Your vacuum pump is the problem. It should easily pull much more than that.

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Rick Miley
2014 Tesla Model S
2018 Tesla Model 3
2017 Nissan LEAF
Former MB: 99 E300, 86 190E 2.3, 87 300E, 80 240D, 82 204D Euro
Chain Elongation References

yes. Leaking diaphragm, it should pull down about 28 in

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

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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'95 E300 Diesel, 264,000 Miles. [Sold it]

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
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"

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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'87 300 TDT (261K)
'85 300 DT (340K +)
'84 300 D (stick, 301K)
'82 240 D (1st one, hooked for good, sold at 325K)

Sounds all to familiar...

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]