Please help, my brakes stop the truck good but not like new, when the truck comes to a stop the pedal then starts to fade on to the floor the truck will creep off if you dont press the pedal on down. Have replaced the pads ft & rr, replaced ft rotors and calipers, also the mastercylinder and hydroboost, still have the same problem. Also replaced the mastercylinder again still same problem, please help.

 

I take it there is no fluid loss?

Are the brakes bleed good? Are they firm or squishy when you push on the peddle?

Most of the time a fading peddle is from a bad master but if you are on the third one that should be ruled out. The last thing to check is the rod adjustment from the peddle to the master, try adjusting the rod a couple turns both ways and see if it gets better either way.

 

Just a shot in the dark - the 7.3's use the PS pump for boost - how's your PS pump? (fluid level & does the truck steer ok)

 

Hey guys thx for your help. I have bleed the brakes twice no air at all pedal is firm and brakes will thro un in the dash, but when it stops and u sit there for a few secs then the pedal starts to fall on to the floor but it will stop about 2" from floor.

 

Brand new PS pump all is fine there

 

From what your describing there must be a leak in the system. Its holding pressure just long enough for it to find a weak spot and then it bleeds off the pressure. Did you check all the rubber lines and all fittings though the system? Ive had a problem similar, one of the hard lines was pinched between the frame and the tank. There was a pin hole just big enough to keep the brakes from working.

 

Hope this helps.

 

Hey thanks so much for your post especially the instructions. Also I have not lost any fluid at all, do yall think it would possible that one of thr new calipers or one of the two olds rr could have a semi seized piston.

 

A siezed piston shouldn't cause the pedal to drop to the floor - should be opposite & make it firmer. Could have a leaky caliper or brake line. Check over the lines going to the rear carefully - they have a tendency to rust and "weap" fluid which can cause the symptoms you're describing. I'd follow them from the master cyl all the way to the calipers. Look for damp spots all the way.

 

did you bench bleed the master before you installed it?

 

yes I bled the mastercylinder before installing and bled the brake system till all fluid came out clear and no air , I have a bleeder for that. Will check the lines, but I have not lost any fluid out of the system none what so ever. I was thinkn that if one of the pistons in one caliper was semiseized it would be hard when I 1st pressed the pedal and then if the piston started moving slowly outward then the pedal would start fading toward the floor. System has no leaks.

 

So you are using a power bleeder? What style? Those power bleeders don't "work" the air bubbles out all the time. Nothing beats a buddy pumping the peddle while you go around and break bleeders loose.

 

With a semi seized piston you would still have a firm pedal all the way to the floor. With all the new parts you've put on did you flush all the old fluid? Brake fluid breaks down over time due to it absorbing water and although its a slim chance that could be the problem. The brakes are a sealed hydraulic system for the brakes to be soft or the pedal to fade there is either air in the line or a fluid leak. If the master, calipers, lines and fittings are fine then its the booster. There is nothing else it could be