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Old 12-30-2007, 12:24 PM
joshhol joshhol is offline
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Join Date: Nov 2002
Location: Flyover State
Posts: 1,364
123 Vacuum Pump rebuild

I'd appreciate some feedback on the direction to take with this vac pump rebuild.
My brother's 1985 300D was only making about 5 Hg vac and not shutting off, no power assist brakes etc.

I pulled the pump, sure enough one of the check valves was cracked.
I installed the parts from the rebuild kit and I think I did it right but put back the pump and still no suction. Pulled the pump back off, checked installation of the check valves. The main check valve at the hose inlet was tested by blowing and sucking. It passed that test by not allowing suction but I was able to blow air through it in the direction of vacuum.

I don't see what could cause it not to produce vacuum. Is it possible that the rings that go around the piston were pinched or compromised on installation?

In perusing the threads, I see that an argument can be made for just putting on a new pump because of the possible devastation caused by the pump arm bearings.
I'm leaning towards that as the car has 275K.

But, I'm just curious as to what would cause my rebuild job to fail.

Thanks
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63 220S W111
76 300D W115
2013 VW JSW TDI M6

previously-
73 280 SEL 4.5
86 300E 5 speed
2010 VW Jetta TDI M6
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