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Prop valve issue

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Old Nov 19, 2021 | 07:50 AM
  #1  
IROCZ1989's Avatar
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Car: 1989 IrocZ
Engine: 421 Dart Stroker
Transmission: 4L60E Cahall Performance Built
Axle/Gears: Midwest Chassis Fab 9/ 3.55 gears
Prop valve issue

Have a fully assembled system on an 89 camaro with the 9 bolt rear pbr calipers. Redid all my lines with conifer from fedhill. All calipers are new, lines are all new because of the special routing on the UMI k member and 9 inch rear. Only thing I reused was the prop amd the Goodridge braided lines. I put in a roll control after the prop valve for nhra spec. I blocked the bottom outlet to the front brakes and used the other to go through the line lock and then split it to the two front brakes. Having issues with the bleeding of the system. Here is the problem. New master was bench bleed 3 times so I know no air is in that. New brake booster. Peddle is hard as anything until vacume is applied to the canister then the pedal goes right to the floor with zero resistance until the vacume is depleted. Pressure bleed, vacume bleed and two man bled. No air from any bleeders. The one issue that has me thinking is the prop valve. When I removed the bleeder that I was using to plug that one outlet nothing came out of the outlet, until I pressed the peddle. The other side that I have plumbed to the tee and though the line lock bleeds no issue what so ever. My plan was to plumb the plugged out to the line lock to get it back in the system. Is the prop the issue or the plumbing? Me bypassing that out maybe caused my issues? I noticed air in that line when I tried to bleed it. At a loss here. Thanks to anyone with imput on this.
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Old Nov 19, 2021 | 01:30 PM
  #2  
Denis.V's Avatar
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From: Santiago, CHILE
Car: 1986 Pontiac Firebird Trans Am
Engine: 305 Tuned Port Injection
Transmission: The famous 700R4
Axle/Gears: No idea
Re: Prop valve issue

What means

"master was bench bleed 3 times" ?

3 "pumps" only or 3 complete bleeds procedures ?

This could be the start point for review and checking





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Old Nov 19, 2021 | 05:00 PM
  #3  
IROCZ1989's Avatar
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From: MA
Car: 1989 IrocZ
Engine: 421 Dart Stroker
Transmission: 4L60E Cahall Performance Built
Axle/Gears: Midwest Chassis Fab 9/ 3.55 gears
Re: Prop valve issue

Originally Posted by Denis.V
What means

"master was bench bleed 3 times" ?

3 "pumps" only or 3 complete bleeds procedures ?

This could be the start point for review and checking
I bench bled it. Installed it same pedal to floor when vacume applied. Rinse and repeat 2 more times. Zero air bubbles all three times. But a search here says air in the master with my symptoms.
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Old Nov 19, 2021 | 06:33 PM
  #4  
Johnny Gun's Avatar
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From: The Peach State
Car: '88 GTA
Engine: 355 SBC, AFR 195 heads, Stealth Ram
Transmission: 700r4
Re: Prop valve issue

My have a tear in the plungers seal on the master cylinder. Mine did that once.
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Old Nov 19, 2021 | 06:40 PM
  #5  
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Car: '89 Firebird
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Re: Prop valve issue

The stock prop valve has a balance bar (or whatever it's called) that gets shoved to one side when there is unequal pressure between the front & rear brake line inlets to prop valve (from master cylinder). Did you go through procedure to center that balance bar? If not, then the front brakes might be partially blocked off.

Sometimes it can be a son of a gun to get fluid moving in a dry system. I tend to open the brake bleeders and let the system just sit for a while and let gravity do it's thing. Seems to help a lot with getting things moving. Pump out all that fluid of course, it's been contaminated with moisture from being exposed to air. And don't let the master go empty or you're screwed and have to bench bleed all over again.

Last edited by QwkTrip; Nov 19, 2021 at 06:46 PM.
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Old Nov 19, 2021 | 08:54 PM
  #6  
IROCZ1989's Avatar
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From: MA
Car: 1989 IrocZ
Engine: 421 Dart Stroker
Transmission: 4L60E Cahall Performance Built
Axle/Gears: Midwest Chassis Fab 9/ 3.55 gears
Re: Prop valve issue

Originally Posted by QwkTrip
The stock prop valve has a balance bar (or whatever it's called) that gets shoved to one side when there is unequal pressure between the front & rear brake line inlets to prop valve (from master cylinder). Did you go through procedure to center that balance bar? If not, then the front brakes might be partially blocked off.

Sometimes it can be a son of a gun to get fluid moving in a dry system. I tend to open the brake bleeders and let the system just sit for a while and let gravity do it's thing. Seems to help a lot with getting things moving. Pump out all that fluid of course, it's been contaminated with moisture from being exposed to air. And don't let the master go empty or you're screwed and have to bench bleed all over again.
I have fluid at every bleeder no air. Whats the procedure to reset the prop valve?
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Old Nov 19, 2021 | 08:55 PM
  #7  
IROCZ1989's Avatar
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From: MA
Car: 1989 IrocZ
Engine: 421 Dart Stroker
Transmission: 4L60E Cahall Performance Built
Axle/Gears: Midwest Chassis Fab 9/ 3.55 gears
Re: Prop valve issue

Originally Posted by Johnny Gun
My have a tear in the plungers seal on the master cylinder. Mine did that once.
its a brand new master cylinder. I hope its not.
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Old Nov 30, 2021 | 01:26 PM
  #8  
IROCZ1989's Avatar
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From: MA
Car: 1989 IrocZ
Engine: 421 Dart Stroker
Transmission: 4L60E Cahall Performance Built
Axle/Gears: Midwest Chassis Fab 9/ 3.55 gears
Re: Prop valve issue

Going to bump this up because I can't find the procedure to reset the prop valve, even if thats it
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Old Dec 2, 2021 | 11:27 AM
  #9  
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Re: Prop valve issue

Generally to reset the brake combination valve after repairs is to stomp on the pedal. The pressure on both sides will center the valve.
Let's start at the very beginning. But 2 brass plus that fit the MC. Plug the MC and see how the pedal feels. If it's hard MC is fine and there is no air. Proceed downstream from there isolating frt. from back and see what you get.
What MC? What size bore? Your MC might not have enough volume as the bore size might be too small for disc calipers you used.
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