Sticking front PBR calliper

[Murd]

I have the 2 piston 99-04 mustang PBR callipers, new from parts store 3 years ago as the used set I had were cursed with the swelling pistons that wouldn’t retract.

Went for a drive today, rare freeway trip, could smell burning brakes, when I pulled off my drivers side front was hot and smoking. Braking performance was definitely sub par but I still had brakes. It was pulling to the right under hard braking, good side, which I’ve never had Before. I was on flat ground and had no trouble rolling the car with it in neutral so it wasn’t dragging too hard.

I let it cool and continued to my my destination as I was almost there. It sat for almost an hour, drove home 30 minutes and no brake smell or excessive heat from the previously sticking calliper.

As I mentioned at the top, I’m familiar with the notorious swelling pistons in these, has anyone had one sticking and then resolve itself?

I haven’t had time since I got home to jack it up and check it out.

Should I just rush out and get a new one?

Are my hawk HPS pads cooked? Do I need to re surface them with some sand paper?

Rotors?

At the least I’ll bleed the brake fluid as I’m sure it’s cooked.

Thoughts?

[Mark K]

I have the same calipers from my '04 Mach 1 donor. Haven't had any sticking problems, but I did rebuild them before mounting them on the chassis, including scotch-bright'ing the pistons and honing the cylinder walls. Very easy to rebuild (and less expensive) using a gasket kit from any of the auto parts suppliers.

[Mastertech5]

If your pads are showing any signs of white they are cooked. they may also look kind of grainy.

[Murd]

Quick update. Jacked up front end and wheel spins freely. Actually more freely than the passenger side.

[SJDave]

I had a similar problem after 10,000 miles and 7 years on the same calipers, bought rebuild kit with new piston and seals, cleaned and assembled. I measured the old piston versus the new phenolic piston and the old was only .001" larger in diameter. The new piston rubber seal was actually .001" thicker then the old one, the old one hadn't swelled and I concluded it's either wear or production tolerances.

Used a piston compressor to push it back in so it would fit over the new Akebono Ceramic pads I was installing to replace the almost worn out Hawk HPS pads and get rid of the brake dust they generate. Re-assemble and bleed the brakes with a vacuum bleeder. Brake pedal is good, no softness nice and hard....go out for a test drive and it doesn't stop worth a darn. Jack up the front, have my wife push the brake pedal hard, both front wheels spin freely, the pistons were stuck back in the caliper bore and would not move out. Well that sucks! So I removed the brake line from the calipers, used a rubber tip on my air compressor nozzle, and shot 100 psi in the piston bore....they POPPED out. Went for a test drive, both fronts were dragging as bad as the old ones I replaced.

So I took them off and used 100 psi to carefully blow the pistons out into a large towel ( be careful if you do this, they will crush your finger if it's in the way.,..I just fold a bath towel up about 4 thicknesses and place it between the piston and the caliper frame (pads Out) and lay the rest of the towel over the top and use my palm to put a small amount of down pressure on the caliper. It will get your attention when it pops out.

The seal is SQUARE, it sits in a round groove in the pistons....that seemed odd. So I called a professional mechanic friend and he said that's normal, the seal is distorted when you push on the brake pedal and acts like a rubber spring to move the pads away from the rotor. I never knew this. So chucked up the pistons in my lathe and ground a cutter to match the groove, and cut it .0015" deeper. Put them back together, no more sticking pistons.

My conclusion is that production and aftermarket part tolerances are all over the place. Honing the piston cylinder opens up that diameter, and probably works about the same to stop the sticking from the pistons swelling .001" in diameter over time. If you get lucky, the piston bore, piston diameter, and seal size can make them work good, but if one or two or three of these is at maximum material condition, a little swelling ....or brand new parts...will stick!!

[Murd]

Thanks for the replies all.
I won’t be rebuilding mine, between work, kids and working on our house to get it ready to sell I don’t even have time to drive the car right now.
Since mine seems to have, at least temporarily, fixed itself, really what I’d like to know from those with experience is have you had a calliper stick and then function properly again?

[GoDadGo]

Thanks for the replies all.
I won’t be rebuilding mine, between work, kids and working on our house to get it ready to sell I don’t even have time to drive the car right now.
Since mine seems to have, at least temporarily, fixed itself, really what I’d like to know from those with experience is have you had a caliper stick and then function properly again?

When time frees up, just pick up a set at your local auto parts store.
Get the lifetime warranty because they may stick again.
Many of us have experienced this issue.
It's a pain, but easy to overcome.

[mcwho]

I have the same issue, just started a few months ago during the deep south cobra clup run. I have the brakes supplied with the complete kit. I smelled the front brakes cooking and stopped and let it cool.thid week i was out for a ride and they started grabbing but didnt get real hot. So if i get a cLiper rebuild kit i ask for s mustang kit for what year, 2000 gt?

[mcwho]

Forgot to mention, i used to own a 2000 mustang gt, same thing, the front roters and wheels smelled like they were burning up. I had the drivers side caliper replaced and sold the caR later. Seemed like same issue.

[mcwho]

When time frees up, just pick up a set at your local auto parts store.
Get the lifetime warranty because they may stick again.
Many of us have experienced this issue.
It's a pain, but easy to overcome.

What I trying to determine is what year make and model do i tell the parts guy to lookup y front brake caliper, rotor and pads, i am guessing a 2000 mustang GT with v-8 (4.6) I looked at the rockauto web pages and did not see any PBR labelled parts. i dont care if i have to replace the calipers rotors and pads, I just want reliable brakes.
thanks

[michael everson]

I wonder why this is happening so often. I cant tell you how many I have had to replace. It did seems like it happened more often if the car sat for a long time. I had a Daytona that sat for 8 years with brand new calipers. They froze the first time I used them.
Mike

[nuhale]

This thread has me a bit concerned. I have the PBR's and they sat in a warehouse for 9 years (without fluid). I've driven 7275 for 1500 miles without issue but for how long... maybe some preventative maintenance is in order.

[mcwho]

I am confused, solution seems to be to replace the calipers when they lock up. Thats NOT a viable solution. can someone suggest honing the caliper piston to some degree that will not lock up. The mustang mentioned earlier sat for about 5 months before they started to overheat. my cobra sat for a few months before the locking up started. maybe the solution (sarcastic) is to remove the calipers and soak them in something when the car is parked.

[michael everson]

I have never heard this problem in the Mustang world. My guess is those cars get driven more. you would think they all would have this problem. The piston is always in brake fluid whether it sits or not. I have probably replaced 20 or more over the years. Most were nearly new.
Mike

[JohnMac]

I’d also be looking at the master cylinder to see if the return orifice is clear. With the brake fluid being hygroscopic (and should be changed annually) it’s possible that a plugged return could cause the problem. Try pushing the caliper piston back and see if there’s a free flow of fluid back to the reservoir.

[SJDave]

I would be more than happy to machine the rubber seal groove in the pistons for you for free....I might even have a couple more new ones on hand. If our interested send me a PM with your contact info.

Oh...to answer your earlier question on which car to look up on Rock Auto...2002 mustang GT is what I used with the V8. Amazon had them too: https://www.amazon.com/dp/B000BZWYBC/ref=au_as_r?_encoding=UTF8&Make=Ford%7C54&Model=Mustang%7C688&Year=2002%7C2002&ie=UTF8&vehicleId=2&vehicleType=automotive

HTH,
Dave


I am confused, solution seems to be to replace the calipers when they lock up. Thats NOT a viable solution. can someone suggest honing the caliper piston to some degree that will not lock up. The mustang mentioned earlier sat for about 5 months before they started to overheat. my cobra sat for a few months before the locking up started. maybe the solution (sarcastic) is to remove the calipers and soak them in something when the car is parked.

[mcwho]

I a still pondering the solution to the front caliper lockup issue. They are 99-2002 mustang gt units. I have lookd at few videos of honing the cyl areas. and researched rebuilt units from rockauto, autozone and others. The rehoning process looks tedious and messy. tgere is a version from cardone that has PHEONOLIC pistons. are those recommended to help the iverheating issue?

yes, or no any why please