|Topic Review (Newest First)|
|06-28-2019 01:15 PM|
|jrflyan||I had the same problem. Check the brake bias. My brake bias bar was catching and not releasing completely. This only happened for the front brakes. Hope this helps.|
|06-27-2019 11:48 PM|
One thing I didn't mention about machining the groove deeper for the seal to sit in, was the groove is actually a "V" shape. Not a square shape that you would expect with a square cross section seal. So I machined it only a few thousands deeper, but created a flat surface for the flat side of the seal to sit on. Does anyone know why the seal groove is a "V" shape?
I also machined the square groove about 20% wider then the seal itself, rubber is incompressible so you need to leave some room for it to grow sideways when it is compressed radially. I guess the V groove allows for that, but just doesn't seem right to me. The V groove would be perfect for a round O-Ring, but seems weird for a square cross section.
|06-27-2019 04:01 PM|
|emac||I spent some time searching the internet and found a thread on a Mustang forum about the phenolic pistons. Several people searched various other cars trying to find a steel piston to replace them. No one ever seemed to come up with a match. Most people just went to another caliper. Others just flushed fluid annually or kept spares. Too bad as it seems such a waste.|
|06-27-2019 03:52 PM|
|Steve Powell||Craig, No help here. They had the SS pistons in them when I got them. I bought them used (very slightly used). They are powder coated red and say "Cobra" in white letters so maybe they are from one of the after market performance brake suppliers. The rears are also red powder coated. Was probably an un-grade kit someone offered.|
|06-26-2019 12:03 PM|
Originally Posted by Steve Powell View Post
|06-26-2019 12:34 AM|
Originally Posted by flip1216 View Post
|06-25-2019 07:50 PM|
Not sure how much you're looking to spend, but I am selling the full front brake set for $275 + shipping. They've never been installed and will include both calipers, mounts, rotors, brake pads, pins, and clips.
PM me if interested.
|06-24-2019 03:34 PM|
|Steve Powell||I've had these on my race car for 8 seasons. I've resealed-rebuilt them several times. I think the difference is mine have steel (stainless steel) pistons. They don't swell.|
|06-24-2019 02:50 PM|
Originally Posted by Greg_M View Post
I took them apart and measured the old pistons versus new pistons and there was only a couple thousandths of an inch difference. Not much swelling but maybe enough. I checked the rubber seals versus new seals and they were identical, no swelling. Hmmmm...thought i would find a bigger issue.
Ok, so put new pistons, new seals, put back on the car....pads won't even come out!!! Really....so pull it apart again, put caliper on the bench, compressor set to 100 psi....after pulsing the pressure for a minute it finally moves out. Ok, so I have a lathe, I remove .005" off the diameter where the rubber seal sits ...reassemble...reinstall....ahhhhhhh...they work now.
I think the tolerances are just not right for the pistons to the bore in the caliper block and the size of the rubber seals, maybe it crept this way over time, can't believe it was designed this way.
|06-24-2019 01:41 PM|
Mine were sticking from the donor. I got decent rebuilt ones from rockauto about 4 years ago and so far they are ok. The phenolic pistons do eventually swell.
|06-24-2019 11:51 AM|
|emac||During my internet search, I found some metal pistons and considered trying to rebuild mine and getting rid of the phenolic pistons. . Once I added up parts and it wasnt much more to buy the rebuilt caliper with a warranty and I wasnt sure a rebuild would evn work. I bet there is a lot of good info on the Mustang forums. I may keep digging.|
|06-24-2019 11:39 AM|
|CraigS||I have a brand new pair I was going to install to replace the heavy cast iron calipers I have now. Bought them last winter. There has been a resurgence in sticking caliper threads so I've decided to forget that 'upgrade'.|
|06-24-2019 10:14 AM|
Same here 2 weeks ago,traded mine for a rebuilt at NAPA up here in Canada.
Seems to be quite common with those calipers...
|06-24-2019 12:53 AM|
I had the same with used ones I bought for my build. They Bothe stuck when I got them installed. Ended up swapping for reman ones like you.
I’d take a min and measure to see it the pistons are square to the “fingers” that hold the outside pad.
Mine aren’t square on one side and the outside pad doesn’t sweep the whole rotor.
|06-24-2019 12:21 AM|
|emac||i decided to pull the caliper and take it apart. I think the plastic pistons must be swollen or warped. They were very hard to get out. Inside was perfect. No gunk or anything. Very hard to get them back in. I ended up going to Autozone and got a reman PBR for $50. Easiest route. If anyone has any pearls about the calipers, I would love to hear them.|
|06-23-2019 06:34 PM|
MKIV base kit PBR brakes issue
I m having an issue with the right front caliper sticking. It is a twin piston PBR caliper. I got it loose a while ago flushed the fluid real good, and it seemed fine until today and it is locked up again.
Thinking of just trying to rebuild it, but I have read where people had issues with rebuilding, so should I just replace it? Best place to buy one? Thanks.