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Discussion Starter #1
I just replaced my brake booster and master cylinder off my 93' today. After bleeding extensively, while running, the brake petal is extremely stiff at the top and if held for a second will soften to normal pedal travel. It will resume stiffness if released and pressed. It feels as the booster is working but I am wondering if I over bled the system. Is that possible? What can I do to correct. Any advice is appreciated.
 

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It sounds as though the brake system's hydraulic circuit is just fine. The vacuum assist on the other hand . . . . well, . . . . sucks. :(

Check to make sure all the vacuum lines are leak free. The vacuum pump that's mounted in front of the power steering pump is of the rotary vane design. A good, reliable pump. Still, with normal wear they loose some performance. If yours is like most, it leaks a little oil as well. One can get a hand-full of seals and rebuild it in a couple of hours (there's a well instructed kit available albeit comparably expensive).

You can better verify the vacuum pump question by simply noting if there's a big improvement with the engine running at a high idle. Having said that, is your idle a bit too low?


Just for good sport, the correct bleeding sequence is:
- Master cylinder.
- Anti-lock control valve (just behind the fuel tank, in the driver's side frame rail).
- Passenger's rear.
- Driver's rear.
- Passenger's front.
- Driver's front.

:)

.
 

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ah no, and vacuum assist on fritz
 

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Discussion Starter #4
Thanks for the info. Any idea what pressure the vacuum pump should be and a good source for the vacuum pump rebuild kit? I will test it tomorrow.
Thanks
 

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A quick peek in one of the FSMs says ~
Vacuum should hold steady in a range of approximately 8.5" ~ 25" at various engine speeds.
Big help huh? :banghead:
 

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it sounds more like the booster is leaking with the truck idling stick your head under the dash and listen for a hissing sound
 

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has any one else thought of swapping to a hydroboost system???
 

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Discussion Starter #9
Checked the vacuum pump and vac. lines were good. Going to re-replace the booster today, any other suggestions?
 

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did you bench bleed the master cylinder before placing in truck that is a critical step as well, everything else these guys are saying sounds good with me too
 
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