C50 brakes seizing after cruising?

[jumpsoffrock]

To start with, when I first get in the truck and zoom off, the brake pedal does what I consider normal--it will depress an inch or two and gain pressure.

After driving the truck for just a few miles with little brake use, the pedal seems to be as hard a friggin rock! It won't depress more than a centimeter if that. It still stops the truck fine, just doesn't seem to have any "give" like every other power brake vehicle I've ever driven.


Then it gets nasty.

All of the sudden after driving the truck for 20-30 minutes, it feels like I'm dragging a boat anchor behind me.....something in the brakes is seizing.
If I put it in gear and take off, I'm at 3000rpm and ready to shift (~12mph), the second I take it out of gear there is so much friction that the truck slams to a stop, as if I hit the brakes.


There is also the smell of burning brakes(obviously).


Does anybody have experience with something like this? How do I diagnose this with the truck cold?

Thank you very much.

[72 5500]

Sounds like one of your rubber brake hoses went bad creating a blockage holding the brakes from releasing. Also could be the booster or master not retuning after you take your foot off the pedal.

[Softpatch]

can you tell which wheels locking up.?
Front.?
Back.?

I don't know jack ... I would say your hydrovac needs bleeding or Rebuild
.

[jumpsoffrock]

Man, I heard rebuilding/replacing these things is impossible.

I'm going to try and see if I can pinpoint it to a certain wheel, after that it's time to investigate the vacuum assist canister.

EDIT: by the way, is hydro assist the same thing as what I have?


Thank you for the replies gents.

[rkn463]

You may have water in the brake fluid, gets hot and boils and creates pressure. Try a complete flush and replace off all of the fluid.

[72 5500]

When the brakes start dragging again, loosen the brake line a bit at the master. if you get allot of fluid and the brakes are free afterwards, the problem in in the master. if the brakes still drag, the problem is some where else.

[jumpsoffrock]

rkn--The fluid is all new and was ran through at least one whole time. But there is a chance.

72 5500--That has got to be the best idea I've seen, would have never thought of that! I'll try it today!

Thank you all very much for the input.

[jumpsoffrock]

Not related to this issue. I blew a front hose today and am going to replace all of the hoses before continuing. It was time to do this anyways.

[72 5500]

Any luck solving the brake problem?

[jumpsoffrock]

Honestly I'm not confident I've driven the truck enough to know absolutely. However, I have driven the truck further than it took to seize up the first couple of times and they have never hardened up or acted unpredictably.


The solution? Carefully and EXTENSIVELY bleeding the entire system 100%. Once we bled it 2-3 times.....we bled every wheel again, just for kicks.


I believe the culprit was a large amount of air in the rear system being superheated by hot fluid, and expanding enough to pressurize the system.
I would really like to get a solid 100+ miles on it before setting anything in concrete though.

[gvw5400]

Just a thought, are the shoes adjusted properly? If they are too tight the brakes work
normally for 15-20 miles then get smoking hot and lock the truck down until it's cool.
Don't ask me how I know this! All the best , Dirk

[jumpsoffrock]

For what it's worth, the last time anyone removed the brake drums the USSR still had control over East Germany.
Long story short, I knew it would be a BEAR to get them off, so I thought I'd try and solve the problem outside of the drums first, and as I said before, I think I may have done that.


No matter what, within the next month or so, I will be removing the drums to inspect the springs, shoes, and replace all wheel cylinders regardless of condition.


Thank you for the info, 5400.

[Peanutbutter]

I bought a C 80 at an auction once and drove it home, almost, got within 3 miles of home and the rears got tighter the farther I went. Had to give it up and park it along side the road. My wife was following me so we went back to the house to get some tools, by the time we got back to the C 80 there was nothing wrong as it had cooled off in the hour we were gone and drove it home the last 3 miles. It took roughly 10 miles for the brakes to get hot enough to expand against the drums and come to a screaching halt. Finally got the drums off and the only thing wrong was the shoes were over tightened, loosened the shoes up and never had another problem.

[jumpsoffrock]

Thank you for the input. How did those drums come off? Is it difficult? Thanks again.

[mrolds88]

Getting the drums off CAN be a pain. Sometimes they come off without incident. Others ya gotta work at. I had at one time a 59 10400 series. Big beast. Rear drums locked and we were to pull it over to the farm about 5 miles away. So I jacked it up, pulled the wheels, then axle, then axle nuts and outer bearing. Now I then took some half inch extensions and built a "spacer" that would push on the end of the opposite axle. Used my harmonic balancer puller (crowsfoot) and it just fit inside the axle bolt circle. Put the needed axle nuts back on, then ran the screw in. When it got tight, took a couple pound sledge and hit around the outside of the drum. Then tightened screw again. After a bit, drums popped off. I stripped the shoes and such then reinstalled everything else. Pulled great.

[carboncrew]

Is brake light switch adjusted right? I've seen when the switch doesn’t let the pedal release, dragging the brakes. The fluid and brakes get hot and expand, making the brakes drag even more - domino effect

Just a quick check maybe worth mentioning.

[jumpsoffrock]

^^^Yes, that was the first thing on my mind--under-dash mechanisms checked first.

Again, I still haven't gotten to drive it far enough to test it.....tires are MEGA TOAST. Thing vibrates like I'm driving on ovals.

[Peanutbutter]

After much thought since my last post I,m starting to get past some CRS. the shoes on my C80 were dragging and the more I drove the hotter they got and the more they locked up. Now I,m remembering the root cause of the problem, I discovered there was no free play in the brake pedal. Whoever installed the brake master had the pedal rod adjusted out to far and the piston in the master was not returning back to the snap ring. If I remember right it took a few tries to get it adjusted just right. I doubt that this has ever happened to anyone else because I always get the weird problems but you never know. the drums can be difficult to get off but some do and some don't.