Caliper problem

[jtexfisher]

Interesting problem with the on '79 1/2 ton. Biggest problem is that the LF brake is sticking. Here's the history.

- Truck has sat for 48 months, +/-.
- Got the truck running, went on test run. LF brake hot, smelly, lots of brake dust generated. Locked up good.
- Attempted to pull caliper, no go. C-clamp etc. would not push piston back into caliper.
- Removed caliper the hard way...used a hammer!
- Replaced caliper with a rebuilt, replaced caliper pins, cleaned caliper mounting areas, bled brakes. Noticed that extreme pressure on the pedal (engine running or not) was required to produce the initial fluid flow to the left front.
- Completed bleed of system, brakes were good.
- On next test drive a sharp stab to the brakes produced the lock condition on the left front.
- Unable to compress piston using c-clamp.
- JUST broke loose the banjo bolt, got a squirt of fluid and the brake released.
- Last 3 can be repeated at will.
- No problem with any of the other 3 brakes.


Anyone seen a similar problem?

jt

 

[gmcman355]

sounds likeyou've got a bad brake hose on the left frt

 

[R72K5]

yep hose sounds like its collapsed

i would replace the other side one also

theyre old and crappy

it happens, i just had to do one on my neighbors 78 c-10 stepside the other day, the right front froze and the truck couldnt move, was stuck out in the street, was an old problme too, ended up needing caliper and shoes and hose and all, and now theres another problem its not getting fluid to the hose even now, something jammed in the system up front, the line blocked or the combo valve messed up, not sure, but the master cylinder is putitng out great pressure and volume out the front port,


it bled a few pumps great pressure out the caliper and then poof, blocked somewhere farther up the system,

so hmm..


old parts, been through hell, sits too much, not driven enough


good luck

 

[Leper]

Something is holding pressure on the system. Hose is probable, and the cheapest thing to check. If that turns out not to be it,you can loosen the line on the input side of the proportioning valve and the output line of the MC to determine where the problem is.
I am dealing with some brake issues myself right now.

 

[pvfjr]

Somethings letting fluid into your caliper at extreme pressures only, and you can't create pressures extreme enough to get it back out. That's why your c-clamp isn't compressing the piston. So like the others have said, you have a bad line.

 

[jtexfisher]

Many thanks to all!

3 new lines from parts is parts at the ready for the weekend.

jt