The Stovebolt Site Forums The Shop Area Driveline Brake job

I dug into the brakes on my truck for the first time to see what I've got. The fronts were in surprisingly good condition. Looks like it had a brake job done not long before it was put away for 17 years. I was able to re-use the drums and shoes and rebuild the wheel cylinders with some honing. There was some pitting in the center of the cylinder but nothing really deep.
The rear brakes were a totally different story. Both wheel cylinders had leaked fluid all over the inside of the drums. The shoes had nothing left on them and it was metal on metal, which cut deep grooves in the drums. I'm getting new shoes and drums for the back tomorrow. Weird how it seems the fluid almost dissolved the brake material and it left a thick paste on the insides of the drums in some places. Here is a close-up of the general condition of the back brakes:

[IMG]http://i7.photobucket.com/albums/y261/bohon/56%20Chevy%20truck/BadBrakes006.jpg[/IMG]

Keep in mind that there could also be leaking rear axle seals which could contribute to this condition. You might also check the parking brake linkage and cables as to the cause for the excessive wear on the rear brakes.
Fred

Good looking spider.

I thought of the rear axle seals and will be pulling the new drums today to see if there is any gear oil in them. The rubber on the wheel cylinders was cracked wide open, so I figure at least some of the mess is brake fluid.
I didn't even see the spider until I uploaded the picture.

that "thick paste" is common, nothing dissolved, just the shoe dust combined with lots of different semi-liquid vapors: road spray, oil fumes, brake fluid .... that pic looks like most old neglected brake assemblies, including the dead spider .... and yes, make sure the park brake mechanisms move freely, they easily get stiff enough to maintain a drag on the rear brakes even tho' you think the hand brake is fully released, your situation of good fronts, thrashed rears can be the result of towing any distance with the park brake sticking, and is one reason the brake shoes should be removed before towing - fires can happen

Bill

OK, I pulled the rear drums and see no sign of leakage from the axle. I will check the emergency brake operation.
I rebuilt the master cylinder and the front wheel cylinders. I honed all of these because there was some pitting, which I didn't entirely remove but I reduced it quite a bit.
The rear wheel cylinders, drums, and shoes were all replaced. I've bled the system twice now and the pedal goes nearly all the way to the floor before there is any braking action and you have to lean on the pedal to stop the truck. On a hard stop, it pulls to the right. I've adjusted all the shoes so that there is a slight drag on the drums when turned by hand.
I checked for leaks and everything was OK. But when I got back from a short drive, I found that the backing plates on the front wheels were wet with brake fluid. I cleaned them off, got in the truck, and pumped the pedal several times. Checked the front wheels and no leaks. Went for another short drive, then took a look at the front backing plates. Wet with brake fluid. I believe there are only two possibilities: The rubber line going to the wheel cylinders and the bleeder screws. But I see no evidence that any of these are leaking.
One thing I noticed while bleeding the brakes. When you pump the master cylinder, it takes a long time to return to its starting position. You can watch through the opening in the reservoir (compensation port?). The piston returns very slowly to its original position. Is it supposed to work like that? Could be I have something installed wrong there. I checked the thrust washer because I know if it's reversed it can block the compensating port, so I'm certain that is in correctly.

I checked the emergency brake function and it seems to be operating normally. The drums turn freely when the brake is not engaged. They lock up pretty tight when it IS engaged.
Where the pedal arm connects to the pushrod at the front of the cylinder there is an eccentric bushing that is obviously for some kind of adjustment. I took a guess on the position of this. Does anyone know how that is supposed to be set up?

Today I re-adjusted all the brakes per the manual. Then I checked toe-board clearance and pedal freeplay. Both good. I used a Mighty-Vac to bleed the brakes again. Found it almost impossible to get any fluid out of any of them. Went around the whole car, then took it out for a drive. The brakes felt really crappy, then gradually started to improve. The more I drove, the better they got. The pulling on hard stops completely disappeared. Now I can hit the brakes, take my hands off the wheel, and it stays in a straight line. I was amazed at the improvement.
I think the seeping at the front wheels is the original bleeder screws, which I reused. I'll be replacing them tomorrow.