BRAKE PROBLEM--HELP!

[ROMPRON]

IM HAVING A PROBLEM GETTING BRAKES ON MY STREET STOCK. IVE BEEN RUNNING FOR ALMOST 2 YEARS WITH LITTLE OR NO BRAKES. IVE PUT ON A NEW SET OF FRONT CALIPERS, NEW STRANGE MASTER CYLINDER, FRONT BRAKE LINES, FRONT AND REAR PADS AND REAR WHEEL CYLINDERS. 2 OR 3 PUMPS AND THE BRAKES OR GREAT, RIGHT ON TOP, BUT WAIT 5 SECONDS AND THEY OR BACK ON THE FLOOR AND THE CAR WILL BARELY STOP. AS YOU CAN TELL IM ABOUT OUT OF PARTS TO REPLACE. THIS IS A 3300 POUND METRIC CAR. ANY IDEALS WOULD BE GREAT.....THANKS

PS.... IF I PUMP THE BRAKES AND HOLD THEM THEY DONT BLEED DOWN AND I HAVE NOT LOST ANY BRAKE FLUID.

[MileHighMan]

Hey Ron. Just my $.02. Either your rear brakes are'nt adjusted out far enough, or you still got air in the lines. Years ago I had a car come in with that same problem, and it turned out to be a slightly bent front brake pad.[ wonder what the person looked liked that did that brake job? Huh, animal] Good Luck,Dan.

[ROMPRON]

THANKS DAN, I ADJUSTED THE REARS OUT UNTILL THE RAER WOULD NOT EVEN TURN TODAY AND IT MADE NO DIFFERENCE. I THOUGHT MAYBY THE FRONT CALIPERS WHERE RETURNING TO MUCH IF THAT IS POSSABLE. IT REALLY SUCKS BECOUSE I HAVE TO BACK OFF WAY EARLY GOING INTO THE CORNERS SO I DONT RUN OVER THE CAR IN FRONT OF ME.

[Transman]

Any residual valve(s) in there?

[MileHighMan]

The front brakes returning too much is exactly what I was talking about. Check and see if you have a pad that is bent. It could be pushing the piston back so you have to pump the brakes up everytime you need them. If not? I would say you got dirt in the master cyl. Good Luck,Dan

[ROMPRON]

THANKS FOR THE RESPONSES,, NO RES VALVES EXCEPT THE BIAS ADJUSTER IF THAT COUNTS.... THE MASTER CYLINDER IS BRAND NEW THIS WEEK.... WHAT COULD CAUSE THE FRONT CYLINDERS TO RETURN TO FAR?

[Transman]

What kind of front calipers do you have? You would certainly benefit from a residual valve for sure in the rear line with drum brakes, which I presume you have by reading your post?

[hotrod]

WHAT COULD CAUSE THE FRONT CYLINDERS TO RETURN TO FAR?

I've heard of folks having problems due to excessive runout on the disks, knocking the pads back instead of letting them drag lightlly on the disk as they are supposed to.

You might want to put a dial indicator on your disks as installed and see if they are not running true. It the disk wobbles slightly as it rotates the high spots will kick the pads back into the calipers every time they come around.

I would imagine the same sort of thing could happen if the caliper is not mounted properly and is free to move around a small amount by rocking. Some are designed to "float" so they self center on the disk, if that floating action is not working because of rust or the system is binding up, the caliper might be slightly off center to the disk making one piston travel much farther than the other to get to the disk.


If the rear drum brakes (assuming you have them) have self adjusters and they are installed on the wrong wheels ( ie left on right , and right on lift) you can have a situation where the self adjusting action pulls the shoes away from the drum over time instead of keeping them properly adjusted.
Larry

[MileHighMan]

You know, looking at hot rods post, makes me remember that it's also possible to get the calipers on backwards. If so,The bleeder screws will be on the bottom. I'm not sure if you can do it on this very car, but maybe something to look at. Good Luck, Dan.

[ROMPRON]

THANKS AGAIN GUYS,,,, BRAND NEW ROTORS, NO RES VALVES (FRONT OR REAR), NO SELF ADJUSTERS, CALIPERS ARE HOWE AND THE BLEEDERS OR ON TOP,,, THE HOWES CAN BE PUT ON EITHER WAY SINCE THE TWO HOLES ARE THE SAME SIZE. THERE DOES SEEM TO BE SOME SLOP IN THEM HOWEVER, SO HOTROD MAY BE ON TO SOMETHING. THE PROBLEM IS THIS HAPPENS IN THE SHOP WITHOUT EVEN MOVING THE CAR.

[Nwguy]

Ron,

Take the pistons out of the calipers, scuff the sides of the pistons with 400 grit and reinstall, be careful with the o rings. Bleed the brakes, and you are ready to go in deep. Some times the o-rings get stuck on the piston,and pull the piston back, when you really want the piston to push thru , and only retract a small bit. Just a shot in the dark, worked on the sportsman car.

[dragv6]

Are you sure there is no air in the system?
Try blocking of the brake lines one at a time with vice grips but not too tight as you can damage the hose & see where the majority of the problem is.
Matt

[awesomebill]

It can 1 of 3 things. Air, which you can either use a pressure bleeder or a vacuum bleederto make sure all air is out.

You can start in the front at the m/c and have someone in the cockpit. Loosen both bleeders or lines at the m/c and get them to push the m/c down slowly and when they are at the bottom, lock the lines off. Do this to allow air to be pushed out and fluid in. When your done there, go to the r/r wheel and do the same thing, open the bleeder, push it all the way down, lock it off. then r/r r/f l/f. This should take care of it. 2. Make sure you do not run out of fluid.

Old brake lines tend to swell sometimes and you could get your spungy pedal with the 3 old rubber lines from the manufactures old lines. Change them out.

3. your proportioning valve is not letting enough fluid to the back or front and the time needed to fill the area behind the piston is to short, If your pedal would bleed down after it was up, I would say you had air.

Also check the air gap in the pads to the rotor themselves. Make sure the bearing adjustment is not to loose, this will cause the cocking and pushing of the piston back.

You did not mention if the rear brakes were disc or shoes? If they are disc, you would need to eliminate the proportioning valve and just install the residual valve for the rear. You have to keep the piston as close to the rotor as possible. These come indifferent psi levels. Make sure you bleed the system properly.

[ROMPRON]

THANKS AGIAN, I PLUGGED THE REAR LINE AND THE PEDAL WAS GREAT SO THE PROBLEM MUST BE IN THE REAR. I THINK ILL DO WHAT NWGUY SAID AND SCUFF THE FRONT ANYWAY JUST TO BE SURE. I FOUND A PINCHED BRAKE LINE AND REPLACED IT AND THAT SEEMED TO HELP A LITTLE BUT NOT MUCH. I REPLACED ALL THE RUBBER BRAKE LINES WITH BRAIDED LINES. GONNA RUN A BUNCH MORE FLUID THRU IT TOMMOROW AND SEE WHAT HAPPENS.

[dragv6]

If the problem is in the rear, have you got the right master cylinder for drum brakes. Thay have a non return valve or somthing in that type of thing that holds a little amount of fluid from returning to the cylinder. May be somthing to check anyway.
Matt