Mechanics

CHEVROLET TRUCK PISTON PROBLEM

1964 Chevrolet Truck

I have a c10 pickup, 1964. The drum brakes were changed over to disc brakes. They worked fine for a while then they started locking yo somewhat. Really getting hot. On one side I found the brake line pluged a little. I opened it up. Next the caliber wouldn't tighten up enough to the rotor to apply enough brake to stop the truck. I decided to put on new calipers. I did. Now
The calipers did not want to go back far enough the get the brake pads unto the rotors. I thought maybe the 2psi. Residual valve may be pluged. I took it off and blew it out. Now I am back to where I was before. Not enough pressure on the rotors to stop by. I have bled the line down good. Do you have any ideas what I can do to correct my problem? The whole braking system is all new.
Dave
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Davetheman6
October 26, 2012.




Residual check valves are for drum brakes only to keep the lip seals in the wheel cylinders from allowing air to come in when the barometric pressure goes up. You never use them with disc brakes. I've never heard of cleaning a residual check valve. The master cylinder is chosen according to whether the vehicle has drum or disc brakes. You also have to consider the bore size of the pistons in the master cylinder. They were matched to the diameter of the rear wheel cylinders. The pistons in the new rear calipers are much larger in diameter but they must move a lot less to apply the pads. I'm not sure how that equates to the size of the piston in the master cylinder. The few times I've seen people do these modifications, everything comes in a kit that someone else already figured out.

If you're using GM rear calipers with the parking brake built in, (a very miserable design), you can't push the pistons back into the calipers. They require a special tool to screw them in. You might be able to work around that by removing the parking brake lever, turning the actuator screw a little, (not too much), then pushing the piston in, and repeating that until it has gone in enough. When you turn the screw it will sink into the housing. You don't want that to go so far that the seal is exposed and air gets in. Push the piston in, then turn the screw some more.

Once the calipers are installed you have to exercise the parking brake to work the pistons out until the pads contact the rotors otherwise they will never self-adjust and you'll have a mushy pedal.
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Caradiodoc
Oct 26, 2012.
Does it have a aftermarket brake booster if not might invest in one if it does check the fluids pressure and all the lines for any damage corrosion or tears

Tiny
Chasewilliams
Jan 30, 2013.
Please take the time to use appropriate punctuation, otherwise we can read that huge sentence at least three different ways.

A booster is not the problem. That just makes the pedal easier to push and that is not the concern here. Damaged lines can't be the problem either. There's no fluid loss. Trapped fluid not releasing is the problem.

Caradiodoc
Jan 30, 2013.

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