The Stovebolt Site Forums The Shop Area General Truck Talk rear brakes, 51 3/4 ton

I picked a bad weekend to start my brake job, with the forum down for repairs and upgrades.
I bought the double master cylinder with booster from CPP for our drum/drum brake system and rebuild kits for all four wheel cylinders.
The first wheel cylinder I take apart has moisture inside, this truck has been sitting for a long time. I tend to be rather safe than sorry and figure I should just replace all the wheel cylinders and probably the lines also. Anyone deal with this before?
I got the CPP master and booster, followed the instructions and when I slid in the booster it was about one inch to far forward to connect to the pedal. I hope I just missed something or someone has a trick to make this fit, I know I could always modify the brackets and slide it back down the frame till it fits but would also like to know why it doesn't fit. any ideas?
Martin

Brake fluid takes on moisture so over time it tends to cause rust if not replaced. Finding moisture inside a wheel cylinder is not good, but not a surprise. Replacing both the cylinders and all the lines is the safe approach.

I'm confused by the booster question. On my dual master conversion too far forward would have made everything too close to the pedal.

OldSub, thanks, The end of the pedal push rod coming out of the booster is about an inch forward of the pedal assembly it needs to connect to. If the brackets, master and booster were moved towards the back of the truck one inch it would line up nicely. It sounds like you didn't have this problem.
I am doing all brakes not just the rear, my mistake in first post.
I guess I'll look into these brake line kits I see in the online catalogs, stainless seems worth the extra cost. Martin

chrmc:
My CPP booster is for 4 wheel disc and not for drum systems. However I wouldn't think there would be any difference in the bracket. Mine fit perfectly. If you need me to make some measurements for you let me know.

Is that rod adjustable? Perhaps turning it will lengthen and shorten it. I used the CPP bracket too, but did not use a power booster. I had no problems with mine.

The rod was adjusted to its shortest length and was still to long. I spoke with a guy at CPP this morning and he had not heard of this problem before, to short yes, to long no. He suggested cutting an inch off of the pedal push rod which should work, the thread inside the push rod looks deep enough to allow for that. I will go over my installation one more time to make sure I didn't make some boneheaded mistake before I bring out the hacksaw. The brackets for these things mount on the two holes that held the original master cylinder on so I don't see much room error.
I have a drum/drum brake system and Classic Auto Parts sent me a booster with proportioning valve which I don't need. You gotta watch these guys. Martin

chrmc
Before you cut check out the pictures on my webshots of my MC.
http://good-times.webshots.com/photo/2933329710099708909JKYdtC

Jim, Thanks for the pictures. Your set up looks just like the one I'm trying to install. It looks like you have the pedal push rod adjusted down to its shortest length. Those locking nuts at each end of the push rod, if I removed those then it might fit. I somehow doubt that would be a good idea. I was also looking at the brake light switch on the firewall. Those screws that come through from inside the cab hold the pedal 1 1/8 inch off the firewall. Is that the same with yours? I think I'll go play with that brake switch for awhile and see if I can bring it closer to the firewall pushing the connection I need farther forward.
Martin

I was able to get about a quarter inch out of moving the brake switch screws in. I found some specs. in the factory assemly manual that want the lower brake assembly 13/16 of an inch from the firewall, so that is now lined up properly. I thought there might have been a failure in the weld at the bottom there but don't see any signs of failure or repair.
If anyone has any ideas or dealt with this in the past feel free to chime in, I can't figure out what's different with my truck to cause this.
In checking the pictures offered by BigChevy I could see the boosters mounting bracket location in relation to some rivets in the frame and mine is the same.
Looks like I'll break out the hacksaw after work tonight. Martin

If you order new wheel cylinders from them be careful. I just replaced master cylinder, all wheel cylinders, shoes, lines, ect. on my '51 3100. I went back stock so I didn't run into the master cylinder problems you're dealing with, but one of the new wheel cylinders I bought from Classic leaked badly. I took it apart and found the pistons inside had been put in backwards. I didn't bother contacting them since it was easly fixed and I wanted to complete the job rather than wait for returns. Classic's always been good to me, I've bought several times from them, but maybe their quality is slipping? Good luck on the brake job.

I finally got a chance to cut the push rod shorter. I had to also cut the threaded bolt cause the threads inside the push rod did not go deep enough. The good news is it's in, I still have to bench bleed the master cylinder, install it, adjust the brake lines and replace the wheel cylinders. Hopefully a bit easier from here on out. There, now I went and jinxed it.
Points of interest
I called back to CPP and was told they have different length push rods for different model trucks, all using the same booster and master cylinder. They offered to find one the length I needed and ship it to me at no cost. I fiqured cutting the one I have was easier, less wasteful.
While I purchased this through Classic Parts of America this item was dropped shipped from CPP. Apparently they only ship with the proportioning valve attached. I tried to sell it back to them, no go.
The hole they drilled and tapped on one end of the push rod was not centered. This seemed like a mistake to me, I could see no reason for it.
I had to modify the bracket that angled over to the frame from the front of the booster, it wouldn't line up so I heat it up and bent it a little.
They supplied a spacer, about a half inch long to be placed on the bolt between the lower brake pedal assembly and the ball (heim) joint on the end of the push rod. I added a few washers to it so the push rod was in a straight line out of the booster. Again, I'm not sure this was necessary but it made sense as I lay on my back looking up at all this stuff.
I may never figure out why this product didn't fit right into my truck like it was supposed to but as I go through other restorations It may be come clear. Martin