The Stovebolt Site Forums The Shop Area Driveline Dragging Brakes

My 46 half ton brakes are not agreeing with me. When I got the truck the master cylinder leaked and it had new wheel cylinders that were not adjusted out so the pedal went all the way to the floor and had minimal braking. I replaced the master cylinder and adjusted the wheel cylinders, but apparently too far out and now have a problem with brakes that are too tight. I have pedal movement of about 2 inches, but when I use the brakes, they heat up and expand to the point of contact. I have adjusted the wheel cylinders in multiple times, yet the problem only seems to get worse (pedal is rock hard with no play to the point it feels like the parking brake is on). After they cool down, no problem. The wheel cylinders are adjusted almost all the way in and it is like they don't return to their original position after applying he brakes. Any ideas, advice, or pointers would be greatly appreciated.

Additional info that may be important: drums all the way around, pads and drums are older (don't know how old), only wheel cylinders and master cylinder are new.

Hy tneely76, when you installed the new master cylinder did you make sure there was some clearance between the linkage and the master cylinder piston? The master cylinder piston must be able to return to its at rest position with some clearance between the piston and the linkage that operates the master cylinder, hope that helps.

If it is only a couple brakes consider...Have you looked at all the brake hardware? Are drums in need of turning? Is it good? Are pads on correctly? Brake pedal return spring good? Brake pedal pivot lubricated correctly? As 3b stated, linkage at the correct tightness to allow piston return?

If all the brakes are dragging, I would lean towards linkage, return spring or in need of lubrication.

Good luck!

Chris

Otherwise and maybe also, confirm that you have new brake lines. If old they may be fouled and quite dangerous.

Thanks all for the info. The brake lines have new hoses to the front wheels, the rear appear to be old. I have been able to bleed all of them so fluid is flowing to the wheel cylinders. I believe it is all the brakes that are dragging since it isn't pulling to one side. Based on what has been recommended, it could very well be the linkage. How can I adjust the it so it will go back to the resting position? Thanks.

Hy tneely76, Your brake pedal should have a return spring on it somewhere, if not purchase one and install it so that the brake pedal comes up against the floor or a stop. Somewhere in your linkage there will be a clevis with a threaded rod and a lock nut, once you have your return spring in place check to see that there is a clearance between the linkage and the master cylinder piston. In other words, the linkage must move a little before it pushes on the master cylinder piston, hope that helps.

Which brake drums are getting hot? Have you checked their temperature with a laser gun?

If the MC pedal adjustment is good, it could be the rear flex line that's acting like a check valve (looks good on the outside, but swollen internally). This would give you even stopping because it handles both rear wheels.

Mike B

You need to think Big Picture when dealing with brake systems on trucks which don't stop on a dime even when everything is perfect.
Start from scratch. Take everything off which is not brand new, including hard lines ans soft lines.
Also, since you are dealing with Huck brakes, there are 2 star adjusters per wheel. Make sure that you are adjusting both of them.

Thanks all for the comments. To follow up on a number of them, there is no return spring attached to the brake pedal. There is an internal spring in the MC which pushes the brake pedal back to the disengaged position. The only external return spring is on the clutch. Regardless, in the current condition, there is no need for one since they are rock hard. Even when they would go to the floor, the pedal always returned to the disengaged position. All the brake drums are getting hot, mild smoking upon returning home from one test run. I have not checked the temp, but it was high enough to increase the tire pressure a couple pounds. When adjusting, I did adjust both sides of the wheel cylinder evenly. I did not adjust the linkage when changing the MC and will approach that next to see if it helps. It will be a little more difficult installed as opposed to having it off the truck. Beyond that, replacing old portions would be my thought. Any other thoughts based on this would be great, I've exhausted my vocabulary list on this one. Thanks.

I own three trucks with stock Huck brakes and all of them have a brake pedal return spring. That spring in the master cylinder is not strong enough. You need one even if that is not the cause of your problem. Based on your symptoms, I think 3B has it right. It sounds like you don't have enough of brake pedal free play. You need to adjust the master cylinder to allow it to release the hydraulic pressure on your system. Good luck,
Kent