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Brakes Dragging

Chevelle_Nut

Chevelle_Nut

Shop Foreman
My Gold 72's front calipers (front disc rear drum factory set up) seem to be dragging more than normal, left side more than right. I have taken the caliper off, cleaned the pads, and lubed the pins. No dice. Brake hoses are new. I replaced the left front caliper and master cylinder. Checked the booster rod length, released the master cylinder from the booster, still dragging. released pressure via bleeder, no pressure in line. I am thinking bad master cylinder. Thoughts
 
Does it drag, then release? Or drag constantly and when stationary, like when you've got the tire off?
 
cheveslakr said:
Does it drag, then release? Or drag constantly and when stationary, like when you've got the tire off?
Click to expand...
I have the wheel off and the left front is very hard to turn, I took the caliper off and the rotor spins free. The piston isn't releasing like it should.

When the caliper was off I compressed the piston, rotor spun free. Applied the brakes, caliper binding on rotor. Left front is worse than the right front.
 
The proportioning valve may be tripped but light isn't on. I am going to try to pull it tomorrow and examine it.
 
You can just pull the center sensor and peek down in. Don't have to dismantle all the lines.
I just bought a $10 centering tool....stick it in where the sensor rides while you bleed the brakes. Keeps it from sticking at either end.
 
cheveslakr said:
You can just pull the center sensor and peek down in. Don't have to dismantle all the lines.
I just bought a $10 centering tool....stick it in where the sensor rides while you bleed the brakes. Keeps it from sticking at either end.
Click to expand...
I have a centering tool, getting the right angle to see in it is going to be tough.
 
Ok, my 2 cars talk. I had to repair on my Bronze Chevelle's combination valve last year, here is the OCS thread.

www.chevelles.com

Combination Valve vs Proportioning Valve -- Kelsey Hayes...

www.chevelles.com www.chevelles.com
1656939105061.png

Maybe they changed the valve in 72 because the one off of the Gold Car looks different than the one in the Pic.

EBay pic: looks like mine:

1656939058857.png

I took the valve off the gold car. I cannot get air or brake cleaner to flow through the front circuit. I have a "mistake" purchased valve from a Camaro that is not correct for the rear brakes, I remember trying it. When I spray cleaner in it the fluid flows through both brake hose circuits. What stinks is I can get to the inside of the block and clean the rear circuit but not the front. There was grit in it. I never "overhauled" it so it may be legacy or when it was blasted somehow grit got in it. Either way I need to have it repaired or replaced.
 
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I removed the combination valve, replacement one came in. I cleaned, tested flow and using air decided to keep the original. Reinstalled, left front still locking. I replaced the caliper this morning and installed new pads (they were cracked). With a basic bleed caliper is not locking. I will recruit a brake pumper this morning and give her a good bleed. Fingers crossed.

I will have a use for the replacement valve I did not use. My bronze Chevelle's rear brakes are locking prematurely, all diagnostics point to the combination valve.
 
I may have posted this deeper in your thread, but I also had a bad new master. Took me awhile to diagnose and now I suspect anything new I buy. Troubleshoot it before you just blindly install. In my case, it bench bleed fine, but wouldn't pump to rear brakes under pressure. Tore it apart but never found the issue, voodoo gremlin that spoke chinese. It's tough to build a hotrod over a few years and find out these parts are garbage when you finally get around to troubleshoot.
 
cheveslakr said:
I may have posted this deeper in your thread, but I also had a bad new master. Took me awhile to diagnose and now I suspect anything new I buy. Troubleshoot it before you just blindly install. In my case, it bench bleed fine, but wouldn't pump to rear brakes under pressure. Tore it apart but never found the issue, voodoo gremlin that spoke chinese. It's tough to build a hotrod over a few years and find out these parts are garbage when you finally get around to troubleshoot.
Click to expand...
Rear brakes are my issue. I had the same trouble with my Bronze Chevelle last winter, 3 bad master cylinders in a row. Very frustrating.
 
Got a NAPA master cylinder, it is pumping fluid. A lot of air in the rear lines, rear drums haven't started to push yet.

My helpers leg is wearing out.
 
I used a hand vacuum bleeder to finally get the air out of the rear brake lines, drums are engaging. Need to get one of my helpers out to do a final pressure bleed before buttoning everything up.
 
Brakes are bled out, wheels on and I took her up the road. First time out front brakes were smoking, I let it cool and drove it again, no smoke, probably new pads. I just drove her again, good pedal, stops great but I still think the fronts are dragging some, probably new pads again. I jacked tit up and can turn the wheels by hand, they just are not very free.

I live on a 55mph country road, easy to do stops and starts on. Before I take her a distance from the house I am going to drive and drive her again until I feel she is good.
 
Chevelle_Nut said:
Brakes are bled out, wheels on and I took her up the road. First time out front brakes were smoking, I let it cool and drove it again, no smoke, probably new pads. I just drove her again, good pedal, stops great but I still think the fronts are dragging some, probably new pads again. I jacked tit up and can turn the wheels by hand, they just are not very free.

I live on a 55mph country road, easy to do stops and starts on. Before I take her a distance from the house I am going to drive and drive her again until I feel she is good.
Click to expand...
The wheels with disc brakes shouldn't spin as freely as drum brakes. But I would think you could spin the wheel a full turn or more.
 
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