No brake pedal with engine on. Help!

[Jack_K]

The car set up in a field for over 7 years and the brake fluid was almost black and one caliper was frozen, so I decided to replace EVERYTHING.

Before I started this total brake replacement overhaul I had working brakes. Just not very good brakes.

I've been trying to bleed the brakes for 3 weeks now. Someone finally pointed out that I might have the calipers swapped side to side. Guess what? Duh!

Now the calipers are on the correct sides (today I noticed a tag that had "Right" on one). Duh! Again.

I have finally bled them and have some pedal. It goes about half way to the floor. I decided I'd adjust the rear drum brakes by backing up and applying the brakes.

As soon as I start the engine and press on the pedal, it goes immediately to the floor with absolutely no resistance at all. If I turn off the engine I have pedal again, same as before I started the engine. With no pedal I can't try backing up cause I can't stop.

What in the world is causing me to lose the brakes when the engine starts.

 

[pontiacgp]

you need to bench bleed the master..

http://www.ehow.com/video_2327999_bench ... inder.html

you can do it with the master installed doing it by the same method using your brake pedal (slowly)

 

[Jack_K]

I did bench bleed the master.

 

[1979ratrod]

same thing happened to me with my elky. so i replaced the master cylinder with a rebuild, worst thing ever! bench bled it and everything and the seals just blew and brake fluid was dripping down the booster. so i put 2 more in and the same thing kept happening so i just bought a brand new one and problem solved.

 

[pontiacgp]

how slack are the back brakes?....did you not adjust them so the drum has some resistance turning by hand? Your back brakes give you your pedal height...and did you reset the proportional valve?

 

[Jack_K]

How do you reset the proportional valve?

 

[pontiacgp]

there is a button on the front of it...I had one that was messed up and the button had to be compressed to get the back brakes to bleed...on another the only way I could reset it was to drive the car backwards and slam on the brakes till I heard it click and until it was reset there was very little in the way of back brakes

 

[GhettoRacingKid]

Never heard of the button on the porpotioning valve, I gotta check mine. the pedal isnt as good as i want it and i just did the the complete rears and just replaced some brake lines and the front pads.

 

[pontiacgp]

the button pushes the piston back to center it...if it's sitting forward the fluid to the back brakes is shut off and you might need to tap it with a hammer to move it back into place..

GM has a tool to hold the pin in it's proper position...

 

[Jack_K]

Exactly where would I look for the proportioning valve? I've never noticed one. I don't see any mention of one in the service manual either.