No Brakes!

[tkremer]

I have a 88 F250 7.3 4x4 and about a week ago I put new brake shoes on the rear, new capilers on the front, and a new master cylinder on it. I bled the master cylinder before I installed it then bled the entire brake system like 4 times and I cannot get the brake pedal from going to the floor. There are no leaks and I am really confused why this is happening, has anyone had this problem before? I dont know if it could be the brake booster or not. Well if you have any info for me I would appreciate it. Thanks

 

[Dirtleg]

Either you still have air in the system or you got a bad Master Cylinder. Someone may correct me but I don't think a bad booster is going to cause it to go to the floor. The master cylinder pistons have to move X amount of brake fluid or compress some air in order for them to move that far. Unless your master cylinder is terribly undersized for your brake system it shouldn't go to floor unless there is air in the system, a leaking caliper/brake cylinder/brake line/hose, or an internal (bypassing) leak in tha master cylinder.

How are you bleeding it?

 

[suv7734]

Sometimes the master cylinder can be a bear to bench bleed, you may need to do that again (how did you do it?). Did you bleed the RABS valve on the left side of the frame under front of the cab? If not there may be air there. You need to bleed the system as follows: right rear, left rear, RABS, right front, left front. The brake booster should not have anything to do with a low pedal. Were there any symptoms before you started the work?

 

[adam g]

Diddo on the bleeding the rabs or proportioning valve. They give trouble when bleeding. Also a guy might check his rear brake adj. That sets your pedal height. These fords rear brakes need to be set pretty tight.

 

[Compu Doc]

When I did my brakes 3K miles ago I replaced the front calipers, rotors, pads, shoes in the rear and all new hardware in the rear including the adjusters.

How I adjusted the rear brakes was to put the drum half way on and turn the adjuster until the shoes were hitting the drum. I then slid the drum on the rest of the way and I have to say the brakes have never been better since I had the truck.

 

[Andylad13]

that seems fine for the adjustment. when the rear is jacked up and you spin the tire you should hear a SLIGHT drag. also you have something wrong somewhere. your pedal should go down like 1/2 way for those rears to come on pretty good, and then it should feel like a damn wall and thats when the fronts have fully come on. if its going to the floor then theres air in it. reason being, air and brake fluid compress differently. air compresses a hell of a lot more. the more air you have in it, the further your pedal will go down. if you dont bleed the furthest from the master first you will never get it all out.

 

[cleithau]

I just put new rear wheel cylinders on my truck, do I need to bleed the RABS valve or can I just bleed the wheel cylinders? I never had any air in the system.

 

[adam g]

As long as the master hasn't went dry from the replacing the wheel cyl you should be able to just bleed the rears. If it has went dry you'll have to bleed the whole system.

 

[MUDKICKR]

what about this, if you put the pedal like 5 times and hold it, where is your petal? if its where it should be then its the rear brk adjustment, if not then its got air in it.

 

[tkremer]

If I pump the brakes about 5 times it builds up pressure and is stiffer, but then it will slowly go to the floor.

 

[tkremer]

I did not bleed the RABS I did not even know about it...I bled the wheels in the order of R rear, L rear, R front, then L front, I also did it with the truck running, I tried to bleed then with the truck turned off but when I pumped the brakes no fluid would come out.

 

[MUDKICKR]

vacuum brks or hydroboot? the way it sounds it had to be vacuum brks. i believe the MC is either bad or needs bled, try using another MC and after you bench bleed it, install it and then bleed it from the lines on the master cyl (the lines you install to the MC) bleeding it that way is a lot easier and after you bleed it there blled it the way you said you did, but let it gravity bleed until fluid comes out. after that you are set. usually you dont have to bleed anything else unless the system went dry completely and most the time even after that the RABS doesnt need bled

 

[riotwarrior]

Too me it sounds like the Rear shoes are not fully adjusted....try this....

While on jack stands....adjust rears till you just cannot turn the drums...then test the brakes...if it still goes to floor...you have air. If not...back the shoes off slowly and when you feel a slight drag, you have hit the sweet spot.

Where the drums turned? If not and they are near max dia, the shoes will take a while to seat and take the curvature, or ARCH of the actual drum diameter as opposed to the arch that they have as replacements.

I remember years ago in the speed shop I worked in they had a shoe arching machine that you would set up for the dia of the drum and arch replacement shoes accordingly to maximize brake shoe contact area.

JM2CW

 

[Double-S-Diesel]

sounds like ya got a bad mastercylinder.

 

[MUDKICKR]

if he pumps the pedal 5 times and holds it, and then it goes to the floor its the master cyl. (or air in the lines somewhere), if he pumps the pedal 5 times and holds it and its a good pedal then its the rear brk adjustment, just that simple