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Brand new rear disc brake pistons not retracting while driving...

7K views 37 replies 13 participants last post by  wtv84 
#1 ·
I just replaced the old rear drum brakes on my 1966 Mustang with a new set of SSBC disc brakes. The front brakes were swapped from drum to disc about a decade ago. While I was at it this weekend, I put in a new dual bowl master cylinder & power booster combination as well as a new distribution block (for 'all disc' configuration). All the brake lines are new from front to back all the way to the caliper at each wheel. There are no brake fluid leaks anywhere on the system. The emergency brake is correctly installed out to each rear caliper mechanical mechanism.

Having shared all of the above, after completing the rear disc brake installation and bleeding the lines, I placed the tires on the car to take her out for a spin. Once around the block and I'm smelling burning brake pads. I wheel back in the garage, get her rear end up on jack stands, remove the wheels and I see that the rotors will not spin freely. I remove the calipers, get the pistons screwed back down into the caliper housings and bolt them back in place over the rotors....Rotors now spin freely. While the car is still up on jack stands, I get in and depress the brake pedal up and down a few times. When I get out and try to spin the rear rotors, they are locked up tight and won't budge. The brake pistons have pushed out against the brake pads when I depressed the brake pedal a few times, but once the brake pedal has been released, I would expect the pistons to retract a bit so that the rotors can spin freely and aren't dragging (and definitely not frozen because of the pistons not retracting at all!).

Appreciate any and all tips/ guidance on what I'm missing here. Thanks!
 
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#31 · (Edited)
289vert, I used the Master Power Brakes BM15201-1 kit. I've looked at the online kit and it shows two connectors that you choose from to connect up to break pedal. I only saw one, but just went out and checked and there is a second one. Fortunately, the one I found and installed is the shorter of the two. I will go ahead and take the M/C off and screw down the adjustment in the morning.
 
#32 ·
Well, it was time. As the 'bit by bit' debugging isn't revealing the 'bad actor', I removed the M/C retaining nuts to loosen it completely from the Power Booster and backed it up about an inch away from the booster and actuating rod. I walked back to check the rotors on the back end and they're are still frozen. I then went ahead and completely removed the brake lines from the M/C (e.g. no hydraulic pressure whatsoever coming from up front through the brake lines). I walked back again to check the rotors on the back end and THEY'RE STILL FROZEN! I'd like to say I've completely removed the M/C & Power Booster from contention as culprits here, now. :)

Given the above, and the fact that I've completely loosened the emergency brake cables and ensured the e-brake attachment is fully released (and the rotors are still frozen!), I'd like to think it's safe to assume that I've isolated the issue to the new rear calipers. Appreciate any of your thoughts, if you feel differently or see something I've missed.
 
#33 ·
Given your diagnostics to this point, I'd be inclined to go back to the vendor and have a serious chat with the "tech" dept. about all of the efforts you've put forth. If they, still, don't have any recommendations to explore, then, I'd be insistent on getting a replacement set. Obviously, they pay return shipping. Could they have been assembled from the factory incorrectly?
 
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#34 ·
How about trying this:
Work you way back from the MC, checking every connection. Loosen them one at a time and checking to see if the rear calipers free up.
Work your way back all the way to the calipers.

I’d hate for you to get new replacement calipers and still have the same problem.
 
#36 ·
I think on that style caliper the pistons rotate "backward". This is to accommodate the parking brake lever. There is a stud that the piston threads into. I don't know if it is possible to mix parts from left to right or if there is any difference. You should be able to install the caliper and check the parking brake operation before bleeding the caliper.
 
#38 ·
They've been anything but easy, that's for sure! :)

As I may be pulling these off and sending them back for a refund, may I ask, "Does anyone have a recommendation for where I can buy rear disc brakes that work on the 1966 Mustang with a 5 lug bolt pattern and will fit with the stock 14" wheel/rim?"...Thanks!
 
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