I just converted my 1974 F100 front drum brakes to disks. I robbed all the parts that were needed from a donor 1978 F150 4X4. I swapped everything from the knuckles out on the axle, the power booster, proportioning valve, master cylinder, the works. I put a new rotor and hub on one side (it was missing), and new calipers on both sides.

The damn thing still won't stop. I have bled the lines 3 times, changed the master cylinder, and checked every conection twice. No luck. I tested the vacuum booster by pumping the brakes while the truck is off, then starting it. The pedal goes down like it should. I put new brake hoses on the front, nothing. Don't get me wrong it does stop, just not well. I cannot lock them up on pavement, and they just kind of skip in the gravel.

My only guess now is that the proportioning valve may have been bad off of the donor truck. Anyone else have a guess???

Dan

 

the proprtioning valve only cuts pressure to the rear brakes, it does not effect the front. I'll have to think about this.

 

Dan, I bought a vacuum tool from Eastwood to help bleed my brakes when I did this swap. It is unbelievable how much air gets trapped in new lines. This vacuum tool really helped, later I used the two man method to finish up. You need to bench bleed the master cylinder before you install it. Are you getting good pressure out of the front bleeder screws? Could it be that the proportioning valve has blocked off the front part of the system (responding to low pressure)and you only have rear brakes? New pads and shoes can take a little use to "set" themselves.
William

 

I did bench bleed the master cylinder, and I do get a good amount of fluid and pressure at each wheel. I am going to check the rear brakes this weekend, I will let you know what I find. Maybe it will be a simple problem but I doubt it, not with my luck. Thanks for the input.

Dan

 

I did bench bleed the master cylinder, and I do get a good amount of fluid and pressure at each wheel. I am going to check the rear brakes this weekend, I will let you know what I find. Maybe it will be a simple problem but I doubt it, not with my luck. Thanks for the input.

Dan