i HAVE CHANGED THE LINE AND CALIBER BUT WHEN I HIT THE BRAKES HARD THE PASSENGER SIDE FRONT BRAKE LOCKS UP. TRIED A SEARCH BUT NO LUCK THEY ARE DISC NEW M/C. THANKS FOR ANY HELP 67 CHEVELLE WITH 70 STYLE CALIBERS. ONLY THING I HAVE CHANGED IS POWER BOOSTER AND M/C BEFORE THAT IT WORKED FINE.

air in the left front?


david

sticking caliper...left front?

david

sticking caliper...left front?

This would be my guess too. Both sides will have equal pressure, but if the left side is sticking, the right do more braking.

I Have Replaced The Caliper And I'M Pretty Sure That I Bled The Brakes. Could It Be The M/c

Could It Be The M/cBoth sides are fed from the same line from the M/C. The pressure will always be equal. If there is air in one side, it will effect both sides the same.

Did you replace both calipers?

Also check front and rear suspension components (springs, control bushings), tire pressure and size, treadwear, make sure front tires match brand/type.
If all checks out good, and Both calipers and lines were replaced, try swapping left and right side brake pads to see what happens. Then also try swapping brake rotors, though that's a long shot.

What Would Happen If I Had Two (2) Proportioning Valves?

If I Release Presure At The Bleeder The Wheel Will Turn, If I Release It At The Proportioning Valve The Wheel Will Turn ( That Is The Line Going To The Pass Side Wheel At Proportioning Valve) If I Release At The M/c It Wiil Not Release. But Looking At Parts I May Have Put Two Proportioning Valves ON ONE OLD STYLE ONE NEW. WOULD THIS CAUSE THE PROBLEM

Help Me Guys !! The Chevelle Needs To Go To The Top Shop But Can't If The Brake Locks Up

why two prop valves?

david

I thought you meant the brake locked prematurely, causing a pull or 1wheel skid, then released. You need to be specific. Your brake is seized and wont release, yes?

If you open the line coming out of the valve, brake releases, and you open the line going in to the valve and the brake remains seized, the valve has a problem. The thing is, it should be going to both fronts, if you have it set up correctly.

You should not have 2 valves in series. It could cause unpredictable braking, though probably not a siezed brake.

Can you give us some more details?

What has been replaced?

What year is it for? (if not original to the car, what did the brakes come from?)

What do you mean by "locking up"? Is it when you hit the brakes, it locks, or is it stuck and won't release?

REason for 2 valves is an oversight. I'm ready to change right now. Once the brakes are applied, the wheel locks up and won't release. The set up is for a '70 Chevelle. The caliper and hose have been replaced. It simply will not release. I'm the wife typing this in . . he keeps calling me the location of the car from his cell phone checking all your replies periodically. Help me out here guys, Thanks, Mrs. Smith.

Got her done guys! Thanks for all the assistance and ideas. Here's what happened: As it turned out, I did have two proportioning valves (1) which was original to the brake system, I removed it. Did not fix the brakes seizing up, continued to look and went to our sponsor Ground UP and looked at proportioning valves and as it turned out, we had two lines crossed on the proportioning valve. Switched the lines and everything is working fine. Again, thanks so much, now we are off to the top shop.

Gary

as it turned out, we had two lines crossed on the proportioning valve. Switched the lines and everything is working fine.

Glad to hear you got it figured out :thumbsup:

I'm curious about the 2 prop-valves. Was one bracketed to the MC, and the other down on the frame? I know I've seen them both ways, and I can't remember which is right for a '70.

Was the disc setup taken from another car, or was it original to this car? If the one on the frame was original from a drum-brake car, it does not do any "proportioning", it is only a distribution block.

You may want to try some panic-stops in an empty parking lot at about 20mph to be sure the rears are not locking up. If you removed one that does the proportioning, and left only a distribution block, it may be braking too much to the rear.

Good Luck :)