This has been driving me up the wall for a few weeks now. A W123 wagon. I have 25in/Hg at the vacuum pump. 25 in/Hg at the end of the hose that connects to the brake booster. I have no Vacuum assist when the hose is connected to the brake booster. New vacuum booster, new hose, new O-ring between the master cylinder and the booster. Even with the two taps on the big hose plugged, I get no vacuum assist. With the booster connected I only read around 5in/HG off the taps that go to the rest of the system.

Where is it leaking from?
What did I over look and not seal.


Any Ideas?

thanks
crackstar

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I'd rather be driving

1983 300TD wagon a.k.a abigail a.k.a. dirtygirl
1994 Chevy S-10 a.k.a. DangerTruck a.k.a. any other string of curse words....

Seems like you have checked everything corrrectly. Check the booster itself with a Mityvac pump. It does take 40-50 pumps to register on the Mityvac gauge but that would be the only thing left.
It is possible that the new booster is bad. A PITA, but possible. the only other place would be the Oring between the master cylinder and the booster.
Again by what you have posted I think the new booster is bad. Vacuum test it.

Dave

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1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car