The Stovebolt Site Forums The Shop Area The HiPo Shop another brake problem

This is a 38 GMC it has a 250 with a t5 trans and a rear end out of a 91 chevy light duty truck. new disk brakes up front (rotors and calibers) new power booster new master cylinder new wheel cylinders and shoes in the rear, new brake lines all the way around. I bleed all the brakes 3 times adjusted the rear brakes, check every where for leaks and only get about a 1/4 pedal but it definitely has some brakes. When I start the engine and press the brakes they go all the way down to the floor and stay there I have to reach down and pull the pedal up off the floor but the brakes will stop me. So could some body give me some ideas where to start looking for my problem I don't have a clue what or where to look. thanks

bleed the master cylinder. I recommend a power bleeder.

If your M/C is located under your cab you should be using residual(SP)? valves. They keep a small amount of fluid pressure at the brakes.

...and proportioning valve

Thanks Scott I will do that tomorrow and Big Chevy thanks for spelling proportioning valve I didn't know how to spell it

alright so I bleed the master cylinder then rebleed the rest of the brake lines again and the brake pedal still has to be pulled up off the floor. My Dad told me to put a spring on it so it will return. The only thing that is not new is the proportioning valve, could it be the proportioning valve that is causing me this problem it was ok on the vehicle I took it off of. Thanks

If you pump the pedal by hand, will they pump up?
Scott

I can't see why the PV would be the problem unless it was stopped up and then it would just restrict brake fluid to the front or rear brakes.

Did you adjust the length of the rod from the booster to master cylinder? Its length is critical. To short and your pedal drops toward the floor and will not return to upper stop. Too long and your brakes will drag. The gap between the ball at the end of the rod and the master cylinder socket is about 1/16", I think. You didn't say, but if you didn't buy the blooster/M.C as a matched pair, the master cylinder sockets are different depths for disc or drum. They sell a "pill" or short rod to make up the difference on the deeper socket type.

48 I now have about a 1/3 of the pedal weather I pump it or not. If I push on the pedal with my hand it will go to the down and return by itself. when I start the engine for the vacuum and push the pedal by hand or foot it will return not the best but it will return. when I put the truck in gear forward or reverse and start rolling and apply the brakes the brakes go down but do not return with out me physically using my hand or foot to return the pedal all the way back up.

Big I agree never seen or heard of a pv do something like that

Beltfed I bought the booster and master as a unit, suppose to come from the manuf. adjusted and it was cheaper then buying the 2 separate units and I didn't want to mess around trying to adjust them

it almost feels like it is binding up on some thing when I am rolling and apply the brakes. I've never had any thing like this happen before that I could not figure out but this has got me stumped

Someone has asked this question but I haven't seen an answer yet.
Have you hooked up the spring to the petal?

Big I didn't know there was a spring on the pedal and that same thing was ask/suggested to me after I posted my last post. we (dad) also think the spring inside the booster might be weak even thought it is a new rebuilt booster. FYI I am going to be putting a spring on the pedal

THANKS for all the help from every body

Body to pedal shaft alignment is critical. I had a problem with my pedal not returning to the top. The problem was the pedal shaft was rubbing on the side of the hole in the floor board.
Check it out.