Rear brakes not building pressure.

[71LS5Formula]

Hey yall. I'm working on my 71 Formula and having a blast with the brakes. The setup is 79 4wd brake booster. Wilwood master and prop valve. New lines all the way through. Caliper hoses are braided 98-02 Trans Am/Camaro. Rear axle hose is from Detroit speed(had/have problems with that) braided. All calipers and rotors and pads are for the 98-02 TA/Camaro. Calipers are rebuilt.

After finding a leak at the Detroit speed hose fitting caused by not being threaded enough to seal to the metal line. I think I may have fixed that. Least no leak now for the moment. I have fluid at all caliper bleed screws. Fronts are building pressure, but the rear doesn't seem to be. I am getting fluid out of them, but not working the calipers. I bleed the master on the car with a clear hose attached to the line from the prop valve and dumped it back in to the master. All the air seems to be gone, so I'm not sure now. Any help will be appreciated. Thanks in advance.



Ben

[ah64pilot]

Did you ever get this figured out?

[71LS5Formula]

Have not.

[andrewb70]

You would be shocked how much fluid a new system will take. I suspect you still have air in the lines. I would keep bleeding the rears.

Andrew

[ah64pilot]

You would be shocked how much fluid a new system will take. I suspect you still have air in the lines. I would keep bleeding the rears.

Andrew

X2

I was going to tell you the same thing. I have also run into a problem with the plunger in the proportioning valve isolating (cutting off fluid) to the rears when bleeding because there was no pressure behind it when I stepped on the pedal. Finally learned to gravity bleed until I have fluid and then start using pedal. If none of that seems to be the problem I would start looking in all the wrong places for possible leaks.

I really hope you get it figured out. My least favorite task on a car is bleeding brakes. Good luck!

[71LS5Formula]

I'm good on leaks. I'll try bleeding again. Thanks yall.

[andrewb70]

I am a big fan of gravity bleeding as well.

Andrew

[71LS5Formula]

I do get fluid through them with a little pressure, but not enough to work the calipers.

[andrewb70]

- - - Updated - - -

I do get fluid through them with a little pressure, but not enough to work the calipers.

This sounds like air being compressed in the line or a leak.

Andrew

[NOT A TA]

For starters I'd take the master cylinder off and bench bleed it properly.

[Apogee]

For starters I'd take the master cylinder off and bench bleed it properly.

X2...the first thing you should do when working on an all new brake system is to bench bleed the MC. I'm a proponent of doing a plugged port bleed, as it will not only bleed the MC quicker than using the recirculation method, but it will also do so providing positive feedback as to when it's fully bleed and confirm function of the MC, both things the recirculation method won't do for you.

Once you've fully bleed the MC, then I would install it and connect one brake circuit at a time, bleeding the circuit before adding anything else to the equation. Too many variables just makes troubleshooting potential issues that much harder, so I typically connect the front brake circuit first, leaving the port for the rear circuit plugged at the MC. Bleed out the fronts and then connect the rears and do the same thing. Do not add move forward until you have a good pedal each step of the way.

Tobin
KORE3

[minendrews68]

what kind of proportioning valve are you using? by any chance do you have a manual? It sounds like there is air in the line, although, if it's air when you pump the brakes and have someone hold down on the brake pedal while you break open the bleeder valve, there should be a short burst of fluid and the pedal will go down. Let us know ..

[71LS5Formula]

I'm going to pull off the master cylinder this weekend and bench bleed it again to see if I get more air out of it.

Proportioning is an adjustable one from wilwood.

[Z06vet]

This may seem obvious, but is the adjusting knob adjusted so that it lets full fluid flow to the rears? If not you'll never get the air out of the rears. Ask me how I know this...

[ctcz28]

Try the Cardone MC bleeding syringe, it's fantastic. Takes about 1 minute to thoroughly bleed the MC. Use a Motive power brake bleeder and the job is a cinch.

[71LS5Formula]

Merry Christmas yall. Got the brakes figured out. Had a massive air pocket in the system. Once I unbolted the master cylinder with the lines connected and leveled it out. Air bubbles came out of both reservoirs. Lots. Must have been stuck. Thanks for all the advice.

[andrewb70]

Merry Christmas yall. Got the brakes figured out. Had a massive air pocket in the system. Once I unbolted the master cylinder with the lines connected and leveled it out. Air bubbles came out of both reservoirs. Lots. Must have been stuck. Thanks for all the advice.

Glad it was something simple. Called it...:-)

Andrew