whats wrong with my brakes????!!!!!

[mrein3]

Originally Posted by Smallz72project

I have never heard of resetting a proportioning valve in my life. The valves on these trucks...at least original valves just distribute the fluid predetermined on how they were made, if its bad it needs replaced. Is it possible that you got the primary and secondary shoes on backwards? I am a certified brake technician for Les Schwab Tire and alot of the time when I have a customer come in that has this scenario and just did brakes on their own have the shoes mixed around. The Leading (primary) shoe should be facing forward and you will notice the friction material is shorter in length then the trailing (secondary). Also check your emergency brake cable and actuating arm, sometimes they get stuck even if you arent using the e-brake.

As far as the swap to 93 parts, can be done. I would assume that you'll need the whole kit and caboodle though all the way to the pedal assembly and if you are using the original calipers and cylinders you can get an aftermarket adjustable prop. valve.

Originally Posted by Huck

THE FACTORY SHOP MANUAL TELLS YOU HOW, WHERE, AND WHY IT IS NECESSARY TO RESET THE PROPORTIONING VALVUE WHEN BLEEDING THE BRAKES. I replaced shoes, master cylinder, proportioning valve, wheel cylinders, etc. Problem would keep coming back (rear lockup). Replacing the brake lines and hoses fixed the problem.

This is EXACTLY why I do my own brake work and don't trust the shops.

When doing major surgery, like replacing front hoses, rear wheel cylinders, or a blown out steel line, you HAVE to hold the button down on the front of the proportioning valve. If you have 3 people, one guy can hold the botton, one guy can pump the brakes, and you can run around cracking bleeder screws. If you don't have that 3rd set of hands, you can simply make the "tool" to hold the botton. All you need is a piece of heavier sheet metal with a tab bent to hold the button and a hole drilled to bolt it to the valve.

Here in the rust belt, ALL leaky rear wheel cylinders, and some front brake hose jobs cost you a brake line job. You can NOT break the line free without twisting the steel line apart (on the rear cylinder - some time ask me how to get around this on the front). The replace rear wheel cylinder procedure usually goes like this:
1. Identify leaky cylinder.
2. Order part and grab a piece of line incase you twist apart what you got.
3. Remove cylinder by twisting and breaking line.
4. Find other end of line you just broke.
5. Cut it flush and use a deep socket to remove it from where it is.
6. Bend up line you grabbed in step 2.
7. Replace wheel cylinder.
8. Hold button on prop. valve so you're not stuck trying to re-center the prop. valve.

Been there, done that about 13 ka-zillion times and only once had to chase around the brake light. I believe I said the same thing when the old timer showed me the button, "I never heard of the button".

Back to the problem at hand - and the reason why I talked about replacing steel brake lines. If I had a 1972 that never had the brake fluid flushed, and I was having issues, I'd make that tool to hold the button, get a friend to help by pumping the pedal for me, and bleed all 4 corners until clear fluid came out of each bleeder screw.

Then I would adjust the rears properly after making sure the shoes are in the correct position.

A 1972 (disk brakes) with fresh brake fluid and properly adjusted rear drums will stop like a 2010 disk/drum truck. It has to.

Oh and check your brake light on the instrument cluster. It may be burnt out.

[66_k10_manny]

I just installed front disc brakes complete with mc and booster on my 66 k10. Kept the rear drum. I installed a new proportioning valve complete with new lines and bled the system. My brakes grab great but the rear brakes are locking up real easily. My pedal also feels kind of spongy, it travels almost to the floorboard. Do you think I might have a similar problem with air in the system or having to reset my proportioning valve? So the button I have to hold down is located the brake sensor on the valve?