Brake Pedal To Floor

Just Started Car, Finally. Brake Pedal Firm When Engine Off. When I Start Car, Pedal Goes To Floor When I Apply Brake And It Will Not Stop Real Wheels From Rotating (on Jack Stands). Is Power Booster The Problem? Pedal Also Is Very Slow Coming Back Up With Engine On. Gary

 

Sounds like your master cylinder. Is it full of brake fluid? You should start with bleeding the brake lines, then if that doesn't solve it, replace the master cylinder.

 

What year? model? Master cylinder could be bypassing fluid internally. If so, master cylinder needs rebuild.

 

Here is a recent thread on a similar problem;

http://www.v8buick.com/showthread.php?t=210018

 

I had the same problem after I did my disk brake swap, but it took several attempts and finally installing speed-bleeders to get the pedal firm again. I'd say bleed the rear brakes until the fluid runs clear.

If you spend $10 and buy a pair of speed-bleeders from Autozone it'll go a lot faster since you can just run a piece of clear tubing off the bleeder into a 2L pop bottle and pump the brakes a few times, top off the fluid, repeat until it runs clear, tighten the bleeder nut and then goto the next brake.

 

I would also check all brake lines and wheel cylinders very closely for leakage.

 

Ok. Here's More Info. I Replace The Entire Brake System. New Master Cylinder, New Booster. There Are No Leaks At The Calipers (there Were Weeks Ago But I Fix Them) The Bleeders Are All up. I Bench Bleed The Master, And Used A Vacuum Pump To Bleed The Brake Again This A.m. I Don't Understand Why The Pedal Would Be Firm With The Engine Off, But As Soon As It Starts, It Goes To The Floor And Is Not Effective?

 

Was your brake system a convert from manual brakes to power? Did you replace your power-master to master cylinder pushrod as part of the replacement parts?

 

Car was originally power drums. Yes I replaced the rod. It flushed up to the back of the piston of the master cylinder. Gary

 

That was something that I just went through with an aftermarket kit. The rod as a little over .100" too long and was not allowing the master cylinder piston to fully return.

 

it was firm because there was no vacuum in the booster.

 

also check your pedal where the rod pins on. you should have two holes that you can pin the rod to. for a power setup it should be pinned in (iirc)the bottom hole. this will make all the difference if it is pinned in the wrong hole.