No rear brakes

[LA 66]

About 8 years ago I converted my 66 F100 short to disc brakes using 70's parts. I was never very happy with the results, but it stopped ok and I didn't have time to fool with it anymore. Fast forward to last month, my other truck was down and I had to pull a heavy trailer to the dump. I could not stop without the trailer brakes. The front wheels would lock up and slide. Running the truck in gear on Jack stands confirmed the rear brakes were not working. Standing on the pedal did nothing to slow the rear wheels.

I replaced the wheel cylinders (stuck) and master cylinder (i couldn't get the old one to bench bleed). Still have the same problem, but with a much firmer pedal. I've bled the brakes multiple times with no improvement. What next?

Background info:

• 67 F100 vacuum booster
  74 F100 master cylinder
  78 F150 beams, spindles
  72 F100 rear drum brakes
  78 F150 combination valve

[Mr. Jones]

From what you described it sounds like the rears just need adjusted out,since you were able to bleed the system there’s pressure back there so your lines must be good......I think these slicks never came with self-adjusters....

[FarmMotorSports]

Does it have the disk drum safety (proportioning) valve on the frame?
If so, is it stuck shut for the rear brakes? have you checked the rubber line to the rear axel for internal damage that is plugging it...

[LA 66]

From what you described it sounds like the rears just need adjusted out,since you were able to bleed the system there’s pressure back there so your lines must be good......I think these slicks never came with self-adjusters....

I bled the brakes with the drums adjusted tight, then backed them off until the wheels could turn with very slight drag. It does have self-adjusters. The rear brakes are the wider 68-75 drums (complete swap - backing plates, axles, etc.).

Does it have the disk drum safety (proportioning) valve on the frame?
If so, is it stuck shut for the rear brakes? have you checked the rubber line to the rear axel for internal damage that is plugging it...

Prop valve - yes. From a 78 F150.

The lines are all copper-nickle that i did when I put the discs on. Hoses were all new then, too.. I get plenty of fluid at each wheel and there aren't any leaks.

[unibody madness]

Have you tripped your pressure differential switch on your brass metering/regulating valve? if you do not have the light switch hooked up, check it with a multi-meter or simple test light hooked up between power and ground .

[LA 66]

Have you tripped your pressure differential switch on your brass metering/regulating valve? if you do not have the light switch hooked up, check it with a multi-meter or simple test light hooked up between power and ground .

I'll check that tonight. What to do if it is tripped?

[FarmMotorSports]

https://www.ford-trucks.com/forums/1446 ... witch.html

This has pictures and some discussion about it.
There seems to be some debate on how to recenter... Or if it should just be replaced. .
If it will not recenter easily, then it may not work when you need it, seems to be the story.