1970 Chevy Chevelle

CSI

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1970 CHEVROLET CHEVELLE

Brakes problem
1970 Chevy Chevelle V8 Two Wheel Drive Automatic

It seems that after the engine is running for a while that the brakes lock up and I can not move the car until I shut it down for a while. I have jacked the car up and the front wheels are deffinitly locked up.
We have changed out the calipers and bleed the whole system. But still does it. I have a 454ci engine which has recently been rebuilt with the power front disc brakes. I did change out the vacuum valve on the booster as well. I'm really stumped at this point.

I will gladly donate more to the cause as soon as my problem goes away.

Thanks, Gary

2 Replies

CARADIODOC

MECHANIC
33,871 POSTS

Hi Gary. Welcome to the forum. When the brakes lock up again, crack open the line at the master cylinder for the front brakes. If they release, suspect fluid contamination or the booster push rod is adjusted too long. (Not all push rods are adjustable). Or you have a brake light switch that is misadjusted and holding the brake pedal down a little. Fluid contaminated with petroleum product will cause the rubber bladder seal under the reservoir cap to swell and be impossible to put back in place. It also causes the two lip seals in the master cylinder to expand past the fluid return ports and block them, trapping the fluid.

If they don't release, crack open a bleeder screw on the caliper. If that allows that caliper to release, look for a constricted rubber hose. Start by the master cylinder and work your way down toward the calipers cracking fittings open until the caliper releases. That will pinpoint the area of fluid restriction.

Caradiodoc