No rear brakes (now working as of 2/13/09)

[FLATBEDFORD]

Kinda stumped on this one. '70 F350 DRW power drums all around. For some reason my rear brakes haven't been self adjusting. Hasn't been a problem as I only drive the truck about 1000 miles a year, I just turn the star wheels a couple clicks every once in a while. Yesterday was adjustment time again. I jacked up the rear, adjusted the rear drums so that there was just a little bit of drag as I usually do. I took it out on the road and jambed on the brakes at about 30 mph. Only the fronts locked. Even in a dirt parking lot the rears wouldn't lock. I went back home, went a few more clicks. Still no rear lock up, but I could tell the brakes were dragging when I drove it. The parking brake holds so I know that the shoes will contact the drums. The pedal is as firm as it has always been. There is plenty fluid in both chambers of the master cylinder. I replaced the wheel cylinders about 2 years ago, maybe 2500 miles. I replaced the master when I bought the truck in Feb '06.
One thing is that I have never been able to reset the brake warning light. I'm wondering if there is a problem with the distribution block. When I bought the truck the rear brake chamber of the master cylinder had almost no fluid and some rust and crap in it. I'm wondering of some of that crap could be lodged in the distribution block. Maybe that is why I can't reset the switch and perhaps its restricting pressure to the rear wheel cylinders. Has anybody ever removed and cleaned one? What do you all think?

[1971ford]

we had a similiar problem on the 71, where only the rears were locking causing us to slide because of weight shifting to the front and the tires in the rear locking and not having traction. anyways, we found that the little piston inside the distribution block thing was stuck. we got the compressor and blew it and now its free. thats probably the problem

[FLATBEDFORD]

That's what I was thinking. I'm not looking forward to getting it out of there. I wonder how many of the brake lines will break when I try to remove them. Should be fun and dirty day.

[1971ford]

my dad removed the 71's, didnt look too fun. good luck
let us know what you find

[69timemachine]

Not sure about how the F350 valve looks, but I've worked on my buddie's brand-X valve and also the '74 power disc valve I put in my '69 when I converted it. The main things I can tell you are to go slow and try not to damage the seals or bend the plunger because they are sometimes hard to come out. Be sure you lay everything out in the orientation that it was removed. Have plenty of brake cleaner on hand and try to have a clean work area. My MC was dry and had a lot of junk in it, so I opened the valve and cleaned it just as a preventative measure. It works just fine with no leaks, so I guess I did a good job. I'm sure you will too. On the warning light, if it's still on after you fixed the valve and properly bled the system, then it may just need a new switch.

[FLATBEDFORD]

I had given up on resetting the warning light and just unplugged it. Maybe after I do this I can plug it back in.

[1971ford]

i forget how my dad and i reset the light exactly, but it only took a minute. ill ask him ask him and see if he remembers. we rolled the truck back and forth or something like that

[FLATBEDFORD]

The way to reset it is basically to bleed both the front and rear brakes until the hydraulic pressure between the two equalize. No matter how many times I did that, I couldn't get the light to go out.

[ToughOldFord]

On the F-350's there another valve mounted to the L/S frame about halfway between the cab and rear axle, IIRC. I do not remember just what it is that it does. That customer of mine that has a '67 F-350 for his daily work truck was telling me he had to replace it and I had never heard of such a thing so I took a look and there it was. Next time I talk to him I'll ask him again just what the heck it's there for.

I got some pics of that truck somewhere...

[FLATBEDFORD]

Never noticed such a thing. I'll have to take a look.

[Jake11]

Wheel cylinders are froze. Rust.

[FORDification]

At this point I think I'd just have a friend push the brake pedal while you go back and crack the bleeder valves, so see if pressure's coming out. If not, then you have line blockage. If you do have pressure coming out the bleeders, then the brake cylinders are froze up as mentioned.

[FLATBEDFORD]

True, I should start by bleeding the rears to check for pressure before I start taking stuff apart. I guess that because the wheel cylinders are new-ish, and because I've never been able to reset the warning switch I'm leaning towards other issues. Now all I need is a day that I can devote to this. This is the 3rd weekend in a row that I have had to work both days.

[two-bit]

You need a buddy experienced with DRW four drum beasts.

Here's the deal... you pay for gas, i'll bring the beer

Good luck Flatbed.

I would check for fluid at the rear also.

I got one of these to come loose on an old J-truck by leaving the rear bleeders open and constantly applying pressure on the front brakes. Eventually it moved and you could then get fluid to all four.
But it took a long time , weeks actually.

Two-bit

[ToughOldFord]

I talked to the owner of that '67 today. He couldn't remember what that valve was for either. Maybe someone shows it in their book(s)?

If I see the truck again any time soon I'll snap a pic of that valve.