To the OP: WELCOME TO THE CLUB! My '93 D250's dash warning lights have come on after one or two pumps on the pedal since I bought it. New master cylinder, total front brake job with rotors, all good stuff from NAPA, no difference whatsoever. Bypass the ABS? That's the whole point: Light loaded rear pickups NEED ABS. Drove the 70 Chevy shortbed for years and know that to be true... Let us know when you find the miracle cure. H

 

My brakes suddenly went low. MC levels were a little low but not to the point that I was concerned. A rear brake adjustment did not help like it had always done in the past. My truck is an early '91 and does not have anti-lock brakes. There is no sensor on the differential, no module under the glove box and no warning light. It, however does have a bleedable rwal valve on the rear frame rail. Would a failure of the valve cause my pedal to go to the floor? It takes about three good jabs on the pedal to get brakes and then they work great. As I have never had anti-lock brakes, I suspect that removing it and removing all of the anti-lock stuff in it and then putting it back might cure my problem.

Any opinions? Up to now, whenever the rear brakes were properly adjusted, my brakes were far superior to those on my F150.

I don't mean to hi-jack this posting but it seemed like you guys were getting at the issue pretty well.

Thanks

 

Ooops. Just looked behind the glove box and there is a black box with bevelled edges and an electrical connector on it. There is nothing on the differential though. The previous owner may have disabled the anti-lock function because he installed a hydraulic trailer brake controller which I understand won't work with anti-lock brakes.

The thinking I'm doing may be a bit foggy but I sure would like some input.

 

I bypassed the whole ABS system and added my own proportioning valve.

 

Thanks, I am leaning that way myself. I rarely drive on ice, usually I have a fair load on ( the truck, not me) and need all the braking available. Your adjustable thingy is a good back-up should I find it twitchy.

 

Maybe someone can clear this up for me. In all of my experience with vacuum boosted power brakes, a booster failure has caused harder, taller pedal with much more effort to get the brakes to work. It can feel like someone put a block of wood under the pedal.

After reading through a number of threads on brakes, there seem to be a lot of people who say their brakes got really mushy when the booster failed. Have power brakes changed a lot or does the power booster do something nasty to the rwal gizmo? Enquiring minds want to know!!!

 

After tooling around with cars and trucks for the last 35 years, I can only say that from personal past experience, that this statement above is correct. I can also say that the opposite is true (for me) that MUSHY BRAKES are a direct result of air in the system, someplace or somehow.

I still have my RWAL valve in place. it's disconnected at the box in the dash, and has been since before I bought the truck. Since I've finally figured out how to bleed these trucks brake systems, through multiple trial and errors on two different 1990's trucks, I've not had any problems with either truck since bleeding the last time. My current truck's brakes were bled last year around august, and have worked perfectly fine since. I utilize my parking brake each time I park (unless it's 20* F or less) and I haven't even adjusted the rears since. Pedal is firm and high as it was supposed to be, and other than my brakes squealing every once in a while, they work great. The ABS system doesn't work, but otherwise, they work fine.

Rear drums need to be replaced or recut, but other than that, nothing to do other than drive it.