Hey guys, I've got an 1989 F150 2WD with and F350 brake swap installed (F350 Booster, MC, and dually rear calipers). I've had this setup for about 10 years, and it worked great...as in you'd be picking teeth out of the steering wheel if you weren't careful. The truck sat for about 4 years, and since then, I can't get the brakes to firm up when I step on the pedal. I've tried 2 MCs, and a new booster, along with an entire brake job all around. I've probably bled 5 quarts through the entire system, thoroughly checked for leaks, etc. I've also gon around and clamped off each of the 3 hoses individually, and one didn't make any more difference in pedal feel than the other. I drove with the rear hose clamped, but not with either of the front 2 clamped (for obvious reasons). The 2 front hoses were replaced before it went on hiatus, the rear hasn't been replaced. I've checked them, and there are no noticeable bulging spots on the hoses. Long story short, I'm running out of ideas. Could my booster be causing this? I have confirmed it's holding vacuum. Thanks for any advice.

Matt

 

No experience with the F350 brake swap, but given all calipers, no drums - any chance of a loose wheel bearing pushing a caliper back in too far?

 

I just went through and repacked all the bearings, put on ceramic pads, and turned the rotors hoping there may have been a problem, but nothing that I can see at all. I still have drums in the rear, just with larger wheel cylinders. Same pad part numbers, along with hose part numbers and all that.

 

Ok, you still have drum brakes in the rear with large wheel cylinders. It sounds like you must have just replaced the rear brake shoes?

Not having a firm or high up brake pedal is a sign of brake SHOES not adjusted up tight enough. If you pump the brake pedal will it come up higher and stay up higher until you let go of the pedal?

I realize you clamped off the hose going to the rear brakes, but did it block off completely tight?

 

I'm pretty sure it clamped it off completely tight, I used vice grips and a rag, and the vice grip jaws are wider than the hose. As far as the shoes, They are new, but the old ones weren't bad, and this behavior happened before I changed them. All of the work I've done has been to try and fix this problem, the pads\shoes\etc had less than 5k on them.

I'll run out and do the pump test. I honestly can't remember for sure.

 

If I pump the brakes while it's running, the pedal never firms up. If I pump while it's off it'll firm up, but as soon as I start it, the pedal will sink (I start it while holding it).

 

Do you have RABS? I had a similar problem with my truck when my hydraulic unit under the cab was failing. I just couldn't get a firm pedal.

 

I do, I have bled there 3 or 4 times as well. How did you end up determining it was the problem?

 

after replacing master cylinder, bleeder screws, pads, ect. it was the only thing left so i bypassed it. then I had a firm pedal again.

 

You just ran lines around the unit or what?