K5 Brakes Holding after Use??

[badbowtie03]

Hey yall,

I have an 87 K5 and when I got it, it had been sitting for about 2 years... anyways... I got it running good with cleaning the tank/new fuel pump and filter... but one thing that it keeps doing is the brakes are holding after you use them. They work good when you press on them but the pedal sticks down and holds it back. Once it sits for about 20-30 seconds they slowly let go and you can easily drive again. If you cut the truck off and hop out and be quiet you can hear the front brakes letting up slowly/gradually. Do yall think this is calipers that are holding or some sort of vacuum line or the brake booster? I am not sure where to start and don't want to throw money at it in the wrong place. Any help would be greatly appreciated. Thanks!!

 

[Wes Harden]

you should take the front calipers off, wire brush the pins. Get new caliper pin o rings and bushings, kit should be less than 15.00. Use silicone grease on the o rings and bushings. Put it back together and see how it works.

 

[badbowtie03]

you should take the front calipers off, wire brush the pins. Get new caliper pin o rings and bushings, kit should be less than 15.00. Use silicone grease on the o rings and bushings. Put it back together and see how it works.

Thats a good idea. Maybe they are just a little corroded from sitting... thanks

 

[Firdaddy]

brake hoses could be collapsed partially as well. they'll act like a check valve and hold pressure in the caliper

 

[eric67camino]

Sticking calipers or collapsed brake lines are valid, however, with the pedal staying down, I would suspect something in the pedal/master cylinder area.

 

[badbowtie03]

Sticking calipers or collapsed brake lines are valid, however, with the pedal staying down, I would suspect something in the pedal/master cylinder area.

So I played with it for a couple minutes this afternoon and Im pretty sure you're right. I just pulled hard up on the pedal and kept pushing it back in and pulled up on it hard again and it actually started to “break free” sort of and was coming up in its own a few times.

 

[eric67camino]

So I played with it for a couple minutes this afternoon and Im pretty sure you're right. I just pulled hard up on the pedal and kept pushing it back in and pulled up on it hard again and it actually started to “break free” sort of and was coming up in its own a few times.

Sweet. Glad you were able to get it narrowed down. I would also recommend going through and check and flush the whole system to be safe. All of the above suggestions are good preventative maintenance and checks.

 

[wasted wages]

So I played with it for a couple minutes this afternoon and Im pretty sure you're right. I just pulled hard up on the pedal and kept pushing it back in and pulled up on it hard again and it actually started to “break free” sort of and was coming up in its own a few times.

Look up under the dash and see if the pivot point on the brake pedal swing arm is rusted up or has dried grease on it... maybe try a shot of PB Blaster on the pivot shaft and the clevis that goes to the booster...does the truck have hydroboost or a
vacuum booster ?

 

[badbowtie03]

Look up under the dash and see if the pivot point on the brake pedal swing arm is rusted up or has dried grease on it... maybe try a shot of PB Blaster on the pivot shaft and the clevis that goes to the booster...does the truck have hydroboost or a
vacuum booster ?

How can i tell which one it has? It does have a vacuum ball looking thing under the hood...

 

[wasted wages]

hydroboost has hydraulic lines going up to a block behind the master cylinder, coming from the power steering pump and steering box....

vacuum booster just has the big round diaphragm behind the master cylinder....

 

[badbowtie03]

hydroboost has hydraulic lines going up to a block behind the master cylinder, coming from the power steering pump and steering box....

vacuum booster just has the big round diaphragm behind the master cylinder....

So yeah it is the regular vacuum booster.. is there diagrams for the vacuum lines to make sure its hooked up right? I do think some vac lines might of crumbled away over time.

 

[Wes Harden]

should have 3/8" vapor fuel line from back of TBI/carb to a check valve on booster, the check vale has a rubber grommet holding it in the boost. This grommet might be hard and split as well