Brake tension

[dubie]

I've now put on approx. 30 miles on my 56 and I seem to have a reoccurring issue. After driving for a while, it feels like the brake calliper is sticking and applying just enough tension to offer resistance. Would this just be air bubbles and I should re bleed the front brakes? It's fine once it all cools down again
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[Speedbumpauto]

RP valves, 2 lb if used, installed in the proper flow? MC adjustment rod from the pedal. If this rod is adjusted too tight so it pushes in slightly on the MC piston when at rest,(do you have a spring to keep the pedal assembly weight from resting on the MC piston?) it closes or blocks the residual pressure port in the MC which is designed to prevent exactly what you describe. I guarantee it will happen, I've done it accidentally on my 1st hot rod trying to get the pedal travel at the exact top. 2 1/2 mile test drive and I didn't think I was going to make it home without a pull over and cool down.

[OrrieG]

I had a similar issue once and found that the MC rod was not allowing the MC cylinder to retract all the way. Pads would heat up and seize the disc. Are you running check valves in the line to the offending caliper?

[mr48chev]

Disk brakes will always have a slight drag as that is how they are designed to work. They don't have any return springs to pull the pads back off the calipers and when you let off the pedal and the 2lb residual valve holds the two pounds pressure on the line you will have that drag.

Speedbumoauto and Orrie gave pretty good suggestions on what may be a possible cause if you have more drag than normal. One more thing to consider is that if you are running a drum/drum master cylinder it may have residual valves behind the brass seats that the brake lines seat on and that may be holding more pressure on the line than you need. If it is a disk/drum mc or a disk/disk mc you should be fine in that department though.

I stole this off the Ford truck board but it shows a Bendix drum/drum master cylinder and you can see the built in residual valve and spring that are behind the seat I mentioned above.

[dubie]

Originally Posted by OrrieG

I had a similar issue once and found that the MC rod was not allowing the MC cylinder to retract all the way. Pads would heat up and seize the disc. Are you running check valves in the line to the offending caliper?

no check valves in the line, it's a steel line coming from the prop valve and connecting to the brake hose and then to the caliper.

This sounds like what is happening with mine. After driving it for 10 minutes the heat builds up and the truck is working harder to push it down the road. By the sounds of it, all I should have to do is adjust the MC rod to allow more travel and everything should work the way it should

[_Ogre]

same as orrieg here. i set up my mc with the stock cab on. between having the cab off and on a couple of times and new mounts, my brakes were dragging and heating up. i diagnosed this by disconnecting the bolt off the stock brake pedal and figure the the mc was slightly depressed. 1/8'' was all i needed to adjust it.

[dubie]

excellent, thanks guys. I'll be taking a look at it tomorrow night and that'll be the first place I check out. I will report back

[dwcsr]

I had a GM that would do a similar thing when it go hot. Turned out to be a bad hose that when it heated up would expand inside and stop the fluid from returning to the master.

[55dude]

Originally Posted by dwcsr

I had a GM that would do a similar thing when it go hot. Turned out to be a bad hose that when it heated up would expand inside and stop the fluid from returning to the master.

X2 first make sure the rod from pedal to MC has clearance. When the caliper starts to drag loosen the fitting where the rubber hose meets metal line and if caliper doesn't back off the hose is collapsed, very common GM truck problem.

[dubie]

These are both brand new hoses.

When I drive the truck when it's cold, everything work and operates fine. After driving for 10 minutes I can pull up behind another car and not touch the brakes and the truck will stop as if someone else is pushing the pedal. Then to get going again i spin the tires to get it up and moving but you can always feel that pressure holding it back. If I leave it for an hour to cool down, everything works fine, until it heats up again. Could it be the brake fluid? or maybe my exhaust is to close to the prop valve? I'm just looking at every angle so when I do get to look at it this week, I have a list of things to check

[OrrieG]

The timing this is the disc and pad heating up and expanding with no where to go but tighter against each other. Something is causing the pads to not withdraw the right distance. They will have a little drag, but to will still coast and not feel like you are braking. Have fun, I hate working on brakes....