Trying to figure out what could be causing my brakes to get stuck on randomly. Brake pedal was very hard and brakes would get stuck on. Could put the car in gear and would have to throttle it up to get it to move. Put it in neutral and couldn’t budge it trying to push it by hand. Could let the car sit a couple days, and then I would be able to roll it by hand again, so I thought this helped rule out a stuck caliper or something. Replaced booster and MC, and this seemed to fix the problem. Pedal seemed normal again and car would start rolling as soon as you let off the brakes. Drove it a couple times with no issues. Cranked it up this evening, and same thing is happening. Won’t roll at all without throttling it up and can’t push it an inch with it in neutral. Any ideas what could be causing this or things to troubleshoot? By the way, it’s front disc/rear drum setup. Thanks for any ideas!

 

What year and model, have there been any modifications?

First see which wheel(s) is stuck. Jack it up and see which wheel is stuck. Crack the bleeder on the stuck wheel and see if the wheel releases, if yes it's hydraulic related possibly a hose. If it doesn't release it's mechanical, stuck caliper, wheel cylinder or Ebrake cable.

Does the car pull under braking, does any wheel get hot?

Good luck!!!

 

Car is a 71 SX Convertible. That was my plan to try and figure out which wheel(s) is sticking. Thanks for the tip about the bleeder valve. Car doesn’t seem to pull when braking. Last time I drove it, the back wheels were cool but the fronts were pretty warm. But the brakes seemed to be fine at that time.

 

If everything is stock, I'm guessing bad brake hoses, they deteriote inside and act like a one-way valve not letting the fluid back out of the calipers.

Good luck!!!

 

A bit of troubleshooting should isolate the cause of your problem as stated above.

 

Thanks for the tips! Hopefully I can get it narrowed down and figure out the root cause. Will keep you updated. Thanks!

 

I think this is exactly what’s happened. The rear drums were the culprit, and as soon as I cracked the bleeder valve, some fluid squirted out and the wheels would spin by hand then. This may be a dumb question, but there is a metal line and a rubber line going into the rear drum. I haven’t traced them yet, but I’m almost certain the metal line at the top is the brake fluid line. But what is the rubber line? It’s more toward the front bottom part of the drum.

 

Well this is going to be one of those times we need a picture. The only thing that may have some rubber on it at the bottom of the backing plate is the e-brake cable.

 

Not a great picture, but it’s all I’ve got for now. Ran out of daylight. Also note that the pic rotated when I uploaded it. The line runs toward the front of the car, not toward the ground.

 

There should be another on the other rear wheel, they should have cables that run to the front of the car.

 

Yep, I think it does. So e-brake cables? That makes sense. Not sure why I didn’t think of that. Thanks!

 

Unfortunately I can't recall from memory neither what the parking brake line looks like as it enters the rear drum brakes (whether it is enclosed in a rubber sleeve) nor can I recall at what location it enters the rear brakes but could it be the parking brake line? I'm looking for a diagram.

 

I guess you guys beat me to it.

 

Yes e-brake cables. Change the rubber hose that connects the metal line from the body to the metal lines on the top of the rear end, you'll need to perform a brake bleed after. You can get one at the local parts store. While your there I would pop the drums off and do an inspection of the brake parts.

 

The diagnostics could be taken another step to determine why the rear brakes retained pressure. It would probably be best to change the brake hoses especially if they are old. If the hoses are changed and it happens again crack the line open at the master and see if there is pressure.
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Is there a residual pressure valve in this system, 71 Cutlass front disc rear drum...anyone know?

 

Thanks so much for the help!

 

None I am aware of. I have reviewed my brake system several times and I only have the combination valve (front disk/rear drum)...'71 CS.

 

If you believe you've narrowed the issue to brake line hoses (in particular), as opposed to some other issue (MC, booster, combination valve, drum, etc.) as Sugar Bear suggested a rotted out hose can act like a one-way valve which allows fluid to run well in one direction but struggles to return in the opposite direction - I suggest flushing the brake fluid in your system and do a complete brake bleeding. This generally isn't required very often and there are numerous opinions on the amount of time and/or mileage to perform a complete brake fluid flush (45,000 miles is what I generally think is appropriate). But, the reservoir can collect water condensation, the water can enter the brake lines, and it's the water which will eventually corrode/deteriorate the inside of the brake lines. If you reside in a high humidity area, the condensation will be even greater. Once you develop corrosion inside the hoses, it's certainly time to flush your brake fluid completely to remove any condensation. Good luck!