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these brakes have me dumb founded

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Old 04-17-2015, 06:25 PM
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Car: 1987 IROC
Engine: 5.3 vortec
Transmission: T56
Axle/Gears: 9 bolt. guessing 3.27:1 ratio
these brakes have me dumb founded

I cant get my brakes to work right. I have an awesome pedal when the engine is off. As soon as i start the car it drops to the floor. Master is new and properly bled, rear calipers are new and they are adjusted pretty well, and the booster is also new.

I dont get it. I plugged the lines to the master and it was fine on or off. I bled the poop out of the whole system. Went through approx a gallon of fluid.

What is causing my insanity?
Old 04-19-2015, 03:15 PM
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Car: 1987 IROC
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Axle/Gears: 9 bolt. guessing 3.27:1 ratio
Re: these brakes have me dumb founded

Now i have replaced the prop valve with an adjustable one and put the front lines on a tee. Same problem. Is there different length pushrods for the booster by any chance?
Old 04-19-2015, 06:37 PM
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Re: these brakes have me dumb founded

If you pump the pedal with the car running does it slowly get hard?
What kind of vacuum are you making at idle at the booster.
does the check valve on the booster work?
Old 04-19-2015, 06:42 PM
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Car: 1987 IROC
Engine: 5.3 vortec
Transmission: T56
Axle/Gears: 9 bolt. guessing 3.27:1 ratio
Re: these brakes have me dumb founded

It does not get harder. The check valve worked when removed from the 2000 suburban doner truck. As far as vacuum goes, i dont have a gauge but it is sucking quite well. i can see the hose suck in a bit but not suck closed.
Old 04-20-2015, 04:31 AM
  #5  
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Car: 86 Trans Am, 92 Firebird
Engine: 408 sbc, 3.1L of raw power
Transmission: TKO600, T5
Axle/Gears: Moser 9", 3:70 trutac, 3:23 torsion
Re: these brakes have me dumb founded

The booster is bad. New or not.
Old 04-20-2015, 07:15 AM
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Car: 1987 IROC
Engine: 5.3 vortec
Transmission: T56
Axle/Gears: 9 bolt. guessing 3.27:1 ratio
Re: these brakes have me dumb founded

I will get that warranteed as soon as it warms back up
Old 04-22-2015, 08:00 PM
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Car: 1987 IROC
Engine: 5.3 vortec
Transmission: T56
Axle/Gears: 9 bolt. guessing 3.27:1 ratio
Re: these brakes have me dumb founded

Replaced booster again, and rear caliper for parking brake not returning properly. No change what so ever
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