'69 camaro vert w/ power brakes, discs on front, drums on rear.

while i was doing the power steering box upgrade, i pulled my power brake booster and master cylinder to clean them up. i replaced the old metering valve with a new disc/drum proportioning valve. i didn't pull any brake lines or brakes off of the car.

now i have everything back together. i've bled the brakes. all connections are tight, and there is not any leaking brake fluid anywhere.

the problem is that the power booster doesn't seem to be working, at least while the motor is running.

i have pedal when the motor is off. when i start the motor, the pedal goes to the floor. each time that i pump the pedal, it goes to the floor. it doesn't matter how many times i pump the brake pedal ... nothing.

there is vacuum to the power booster.

what did i do wrong?

the new proportioning valve is from classic camaro. should i have done something to this prior to installing??

it seems like there has to be something simple that i'm missing. anybody got any ideas??

thanks

Sounds like you still have air in the system. I'd pull the MC back off and bench bleed it, reinstall, then bleed the system again.

When you start the car does it actually pull the pedal to the floor?

I'v seen that happen when the booster had an internal leak to atmospere all the time.

no, it doesn't pull the pedal to the floor. but when i push the pedal, it will go to the floor. the brakes will hold the car, but the booster simply isn't there.

if i pull the vacuum line from the booster, i can hear the pressure release. so i'm fairly sure that the booster is holding vacuum.

i bench bled the m/c before i put it in, and then bled the brakes with the normal procedure, starting at the farthest brake.

was there something that i should have done to the new proportioning valve during the bleeding procedure? i do notice that my dash brake light is on as soon as i start the car. and it pulses as i push the pedal.

i'll try bench bleeding the m/c again, and bleeding the brakes.

Do you think you have to repress the little plunger behind the restrictor? Not the dist valve, Some have these,, mine does. Never knew what it was. Its the round valve thingy that some people have on the frame below the drivers door, feeds the rear brakes. That may have something to do with the spongy feel? you should be able to pump up brakes with eng off, upon starting, your pedal will go down more, that should tell you your booser is working. What about your booster vacumn check valve, is it holding?

no, it doesn't pull the pedal to the floor. but when i push the pedal, it will go to the floor.

When the pedal goes to the floor, there's either air in the master cylinder bore or the piston seals are shot and it's bypassing fluid internally. That's independent of the booster issue.

:beers:

well, i bled the master cylinder again, but it was apparently in good shape.

the new proportioning valve instructions include a blurb on "tripping" the valve, and if it's tripped, how to recenter it. which is essentially bleeding the brakes on either the front or the rear ..... which ever one already has flow. so that's what i'll try next.

so, to end this thread up ......

the new proportioning valve was apparently "tripped" during my inital bleeding of the brake system. which means no fluid to either the front or rear brakes, plus the dashboard "idiot" light was on indicating low fluid level. i got that reset, bled the brakes again, and it all seems to be working fine.

probably another "cause" of the brake pedal feeling different from before i started all of this was the fact that i left the small return spring off of the brake pedal. my car has had this spring in place for years. i read through a thread here on the site that indicated that the power boosted brake system does NOT utilize the return spring on the brake pedal. so i had left off.

anyhow, i seem to be back in operation. the new proportioning valve keeps the rear drums from locking up before the front discs.

thanks for all of the help.