Rear brakes locking up?!

[Brown_Muscle]

This applies to aero rear disc brakes on my 89 colony park.. I was driving home today and something went very wrong with my right rear brake. When stopping at higher speeds it would make a lot of noise, almost like groaning/grinding. At lower speeds coming to a stop it would basically lock the rear wheel up and make it hop along the ground. When I go to accelerate from a stop I would have to give it a lot of gas and it would go POP and offer no more resistance until i tried to brake again. When driving it makes a high pitch squealing noise, almost like the low brake indicator, however the pads are almost new. I tried it in reverse however it exhibits none of these symptoms while driving in reverse.

The axle doesn't appear to have excessive play, the wheel adapter i have bolted on there was tight as can be, and the wheel itself was tight. I was able to remove the caliper with almost no resistance... I'm suspecting the caliper might be bad (its a reman unit, only a few years old), however I've never had a bad caliper do this. Any ideas/anyone experience anything like this?

Thanks
-Phil

[87gtVIC]

Im suspecting caliper as well. If not caliper then what is feeding the caliper....master cylinder could be telling it to do funny things.

[Brown_Muscle]

I would think that would effect both sides though if it were the master cylinder though? I should mention that the right side was also hotter than the left side

[jaywish]

In that order, Caliper, Master.

Are you using stock master?
If so did you permanently disable the pressure control fitting on the side of the master that the brake line screws to?

Hoses can collapse but that would usually present as drag after pedal released.

[jaywish]

Doyou have one hose over the rear and hard lines to the calipers?

Does sound like caliper is fubar'ed.

[Brown_Muscle]

It is a stock master, I have no idea if the pressure control fitting was disabled or not. i actually have a new booster and 98-02 master to go in the wagon, just haven't gotten around to it.

I do have a hose over the rear and new hard lines going to another flex line going to the caliper. All the hoses are a few years old, and all the hard lines are either new as of a few months ago, or new as of a couple years ago

[jaywish]

By flex lines do you mean hoses or something I'm not familiar with?

Calipers are cheap. Get a caliper, with new bolts, boots and slippers, pads if you think you might need them. (hose also if that is what you mean)
Hopefully it will become obvious once you take it apart.
I recently had rust bubbles under the stainless slipper. I think it was causing uneven pad wear. So clean the brackets well and lube them under the slipper.
I would double check the E-brake stuff while I was there, just cause.
You can always return the stuff if you take it apart and find something else.

I like these Extended wear pads both fore and aft on our panthers.

https://www.rockauto.com/en/moreinfo...8370&jsn=18716

[87gtVIC]

Heat means friction. Only explanation is that side is grabbing more.

And yes, I would imagine if something is up with the master it would cause both rear brakes to function abnormally and not just one.

[gadget73]

Something is dragging, could be parking brake and not service brake though. Gonna have to pull the wheel for a look. Take the rotor off and check inside too.

[Brown_Muscle]

Yeah, the parking brake seemed to work ok overall, I used it to stop several times on the way home. I ordered 2 new raybestos professional grade calipers that were on closeout from rockauto for $17 each. So we will see what that ends up doing.

[jaywish]

don't forget to check whatever that flex line is.

[Brown_Muscle]

Ah yeah, flexible brake line= brake hose

[86VickyLX]

In that order, Caliper, Master.

Are you using stock master?
If so did you permanently disable the pressure control fitting on the side of the master that the brake line screws to?

Never had that problem on my 86. And it certainly wouldn't cause lock up on one side.

[gadget73]

It will make for slightly premature wear on the rear brake pads, but thats about the worst of it.

[His Royal Ghostliness]

If she rolls easy after a drive (hot rotors & pads) then caliper ain't dragging. If caliper ain't dragging it's got no reason to grab and hop, brake torque is a function of line pressure and the caliper certainly can't make its own pressure. Master cylinder makes the pressure, but it's not side-specific, just axle-specific - meaning both calipers on each axle will be acting up, not just one. Also that pressure valve has never been an issue, and if it ever does become one it will affect both wheels, not just one.

Pull the rotor, inspect the parking brake. Wouldn't be the first time a non-riveted friction delaminated from its steel backing and got jammed where it don't belong causing issues.