PBR Front Brakes - Pistons won't retract

[NA5KAR]

I spent last Saturday trying to diagnose a problem with my front brakes. As I've mentioned in a couple of recent posts, my Mk4 build was neglected during busier times of work over the past couple of years. I've been back at it for a few months and did a bit of go-carting around the neighborhood. On the latest run, I approached the driveway and put the clutch in. The car stopped. It felt locked up. I was able to back into the garage, but it did feel like the brakes were fighting me. Got the car onto jack stands. Both front tires needed considerable effort to rotate. The back tires would rotate much easier than the fronts. I removed the front tires, and on the driver's side, I cracked the caliper bleeder. Got a little fluid flowing. The goal was to relieve the pressure. I still needed a prybar to rotate the rotor. Same thing on the passenger side. So, I removed the caliper lower bolt and flipped the caliper up. I used a brake piston retraction tool (don't know what else to call it) to push the pistons in. They went in ok and came back out when I pushed the brake. So, I pushed them back in and flipped the caliper down and put the bolt in. Pushed the brake and the pistons engaged the rotor. But they didn't retract. Couldn't turn the rotor.

Now it was time to have a conversation with my buddy Chat GPT. After all of the back an forth, I asked "this car has about 25 miles on it. The brakes are new. Is it possible that the brake piston seals that are supposed to allow and help the pistons to retract have deteriorated due to lack of use for a couple of years'? Well, Chat got very excited and told me that it was not only possible, but highly likely. I tried adding some brake caliper approved lubrication under the dust boots to 're-lubricate' the seals. Then I exercised them a few times. Did not help at all. So, I need to rebuild my front calipers to get good seals and lubrication working for me again.

Would love to read any comments. Mostly, I would like to know if anyone has a good source for the rebuild kit for the PBR brakes supplied by FFR. Thanks for reading.

[mrglaeser]

This same topic I think came up this morning for another forum member. I haven't watched it but it looks like they put a video series together on troubleshooting their brakes.

https://thefactoryfiveforum.com/showthread.php?27544-40-Watt-Garage-amp-9365/page14

[NA5KAR]

This same topic I think came up this morning for another forum member. I haven't watched it but it looks like they put a video series together on troubleshooting their brakes.

https://thefactoryfiveforum.com/showthread.php?27544-40-Watt-Garage-amp-9365/page14

Thanks for the heads up! I started watching the videos and it seems like I'm about to learn something important. I'll finish them in the morning. Appreciate the link.

[cc2Arider]

Did you check your adjustment rod for your front brake master cylinder? The Master cylinder rod needs a little freeplay since there is a very small bypass orifice in the piston bore...expressly for the purpose of relieving built-up pressure in the system when the pedal is not pressed...

Craig C

[CraigS]

Also check that the brake pedal arm isn't hitting the small frame cross tube when you are off the pedal.

[rich grsc]

He said he released the pressure by loosening the bleed screws. PBR are notorious for seized pistons, not the seals

[OSU Cowboy]

I took 11 years to get my MK3.1 on the road in Nov 2019. 500 miles on the car. Talked my wife into getting in the car for a short drive for the first time. About 2 or 3 miles out she smelled something. Long story short, the PBR calipers were locked down hard on the front rotors. I managed to get it home, had to replace rotors / calipers / pads.

Do yourself a favor and replace the PBR calipers - now. Don't mess around with trying the make the ones you have work. They are not that expensive.

[NA5KAR]

Did you check your adjustment rod for your front brake master cylinder? The Master cylinder rod needs a little freeplay since there is a very small bypass orifice in the piston bore...expressly for the purpose of relieving built-up pressure in the system when the pedal is not pressed...

Craig C

Thanks Craig. During my diagnosis process, I had a buddy over and that was his primary focus. He wanted to make sure that the plunger in the master cylinder was retracting enough to allow the fluid to return to the reservoir. We can wiggle the plunger and move it slightly in and out of the MC. Also, (didn't mention this in my post) when the caliper was tilted up away from the rotor, we pushed the brake pedal to bring one of the pistons out a little further (clamped the other piston). We watched the fluid in the reservoir go down a little. Using my brake tool, I pushed the piston back in. The fluid rose to the previous level. I think this tells me that the return mechanism is not blocked. Thanks

[NA5KAR]

Also check that the brake pedal arm isn't hitting the small frame cross tube when you are off the pedal.

Thanks Craig. I'll check that specifically tomorrow morning when I get back in the garage.

[NA5KAR]

I took 11 years to get my MK3.1 on the road in Nov 2019. 500 miles on the car. Talked my wife into getting in the car for a short drive for the first time. About 2 or 3 miles out she smelled something. Long story short, the PBR calipers were locked down hard on the front rotors. I managed to get it home, had to replace rotors / calipers / pads.

Do yourself a favor and replace the PBR calipers - now. Don't mess around with trying the make the ones you have work. They are not that expensive.

Thanks OSU Cowboy. In my little post here, I see a couple remarks about the PBR calipers and their pistons. I don't want to put a band aid on a problem when I can cure it with a little money. I would be happy to replace all four calipers with a higher quality set. Any recommendations?

[nuhale]

Powerstop KC1304D

[rich grsc]

No need to replace all 4, only the fronts are PBR's

[NA5KAR]

Powerstop KC1304D
Thanks for the referral. Just placed the order.

[VdubJoe]

Had the exact problem with mine. Worked fine when i first installed them. Then car sat for a good while. Front would not retract. Took them apart . They have phenolic pistons and they were seized. I got them apart and replaced the pistons with stainless ones i found on rock auto. Work like they should now.

[John Ibele]

^^ beat me to it …

I had the same problem with a front brake before I got my MK4 on the road, but after I had powder coated my front calipers. I found a brake place that rebuilt and cycle tested overnight, all for under $100. Cheap way to go and 5000mi and two summers later it’s working fine. So a cheap and solid solution for me. However …

IIRC from when I dug into the issue it was a pretty common problem with those PBR dual piston brakes either due to the material selection for the pistons (phenolic) or someone hadn’t done their geometric dimensioning and tolerancing homework on the supply chain for the brakes. So if it happens again I’ll go nuhales route and get the Powerstop upgrade. Less fade and no reported issues like the PBRs.

[NA5KAR]

Also check that the brake pedal arm isn't hitting the small frame cross tube when you are off the pedal.

The brake pedal is not hitting the cross tube. Tiny movement in the MC pushrod. When pushing the pistons in with the tool, the brake fluid rises in the reservoir. Several comments about the PBR known issues. I don't want to wait for the inevitable day when I have to call for a tow. I went with the 'buy new front brakes' plan. I ordered the Powerstop. Thanks to everyone for the conversation.

[Cutter 54]

Powerstop KC1304D

To Nuhale, John I and NA5KAR;

I also have the PBR 2 piston front set with 11" rotors and 1 piston rears with 11.65" rotors. I want to replace the PBRs. I have 17" inch wheels all around and do not plan to track the car. I use a FOMOCO power booster for brakes and steering.

Regarding the above Power Stop brakes, the kit is available as

-#KC1301-26 "Street Warrior". (Z26 track pads, Red powder coated calipers, slotted and drilled 10.9" rotors),
-#KC 1301D23 "Evolution Sport" (Z23 performance pads, Red Powder coated calipers, slotted and drilled 10.9" rotors)
-#KCOE1301 "Stock Replacement". (stock pads, no powder coating, solid 10.9" rotors).

In addition, my rear brakes overheat apparently due to poor retraction of the emergency brake cable when the e-brake is released due to binding of the small, spring loaded arm on the caliper. I decided not to remove and clean them up. I worry about getting the springs back in place.

There are many Power Stop options for REAR brake kits since there are several 2015 Mustang models. Power Stop kits correspond to various Mustang models as indicated by FRONT brakes. These include EcoBoost with 2 piston front brakes; EcoBoost with 4 piston fronts, Mustang GT with 4 piston fronts, GT with 6 piston Fronts, Shelby GT350, 350R with 2 piece rotors and V6 models. Like so many parts on the Roadster, there are numerous possible solutions.

I figure the Mustang GT with 4 piston front calipers would work. The corresponding Power Stop kits offered for the REAR brakes (2015 IRS on my car) are;

-KC6812-26 "Street Warrior" (Red powder coated calipers, Z26 pads, drilled and slotted 13" rotors),
-KC6812 "Evolution Sport" (Red powder coated calipers, Z23 pads drilled and slotted 13" rotors ),
-KCOE6812 "Stock Replacement" (Gray non powder coated calipers, stock pads, solid 13" rotors).



Two questions: 1) I won't track the car, so are the Z23 pads adequate, vs Z26 pads?
2) Is there a problem installing 13" rotors to replace my 11.65" rear PBS rotors?

Thanks in advance. I don't want to order the wrong sets. Ed K

[nuhale]

Should have noted that the front brake kit I provided will only work with 17"+ wheels. I've used these on both my builds and the z23 have been fine. Only difference I can see is a metal shim on the pad on Z26. Both listed as same composition. The 13" rotors fill the dish so much nicer and give more brake. I used the powerstop 15+ IRS brakes on my current coupe build but can not speak to fit on 17" you have as I'm using custom Forgestar 19" wheels. I can tell you that the rear will not fit 17" FR500 mustang wheels but no clue on 17" FFR Halibrands. They will require different ebrake cables.

I have the 13" fronts and 12.88?ish single piston FFR brakes on my MK4 with 17" Halibrands and it's more than enough.

[Cutter 54]

Thanks for reply.
Now the Coupe has IRS and ?15” rotors? Is that what you mean? If so I will have no problem with the Halibrands as I would be fitting 13’s on the rear and 10.9’s on the front.
You mention needing different e-brake cables on the coupe. Can you tell me which calipers you have in the rears? As I indicated I am looking at PowerStop KC6812 calipers for the 2015 Mustang IRS. Is the cable issue about length or attachment to the caliper body?
Don’t mean to pepper you with questions but after a 4+ year build I am crazy with sweating every detail on this car and want to be DONE. Thanks.
I will stick with the Z23 pads.

[John Ibele]

Thanks for reply.
Now the Coupe has IRS and ?15” rotors? Is that what you mean? If so I will have no problem with the Halibrands as I would be fitting 13’s on the rear and 10.9’s on the front.
You mention needing different e-brake cables on the coupe. Can you tell me which calipers you have in the rears? As I indicated I am looking at PowerStop KC6812 calipers for the 2015 Mustang IRS. Is the cable issue about length or attachment to the caliper body?
Don’t mean to pepper you with questions but after a 4+ year build I am crazy with sweating every detail on this car and want to be DONE. Thanks.
I will stick with the Z23 pads.

A few thoughts -

Front Brakes:

Brakes are one of those things you really don't want to engineer on your own. Use a proven configuration, either the stock kit offering or an alternative front / rear combination that has been proven to work by one or more trusted resources on the forum. I addressed my PBR front brake issue and since then I have had no problems and feel like I have plenty of stopping power for any sort of use on the street. If I had it to do over again, I would do what NA5KAR is doing and just order the Powerstop 1304 kit mentioned above. But if you're really interested in getting on the road, and the front brakes already work as they should, I would leave them for now. And those are 13" front rotors in that 1304 kit, not 10.9s as you indicated - at least based on what I see in Summit's specs. You want more stopping power in front, and enough stopping power in back to transfer the weight to the front. The further you deviate from the rotor selections in the kit, the more likely you are going to throw other things out of whack (balance bar, master cylinder diameter ...). Back to my first comment on not engineering anything fundamentally new.

Rear Brakes:

Any work you have to do to get the current rears working as they should will be less work than buying a new kit and getting that to work. I spent a lot of time getting the e-brake cable routing looking like I wanted it to, with clean operation and retract. I fabbed and inserted a bracket to keep the cable away from the inner radius of the wheel, added a snap ring where there wasn't one. Eventually I got something I was confident I could put on the road.

Hope that helps some.

[Cutter 54]

Well thanks John. I notice the Powerstop KC1304 brakes are for a 1994-98 Mustang GT. I was under the impression that the front brakes on a Mk4 should be from a 1999-2004 Stang. Please confirm. I just ordered the KC1301 set from the fronts and KC6812 for the rears. Waiting for arrival soon.

The reason I bought new front and rears is because I have been disappointed in the PBR brakes from the FFR compete kit and was advised the Powerstop products are very good for my purpose. I have tried to do my own investigation but often make simple errors. I hope the KC1301 calipers fit and I won't have issues with the e-brake cable.

If the above plan fails, you will hear a piercing, very loud roar coming from the South East. (currently in Central Florida) Ed K.

To be continued.

[John Ibele]

... Please confirm.

Don't wait for confirmation from me. :) Reason is: no special magic here. The usual drill ... ask questions, dig into specs, call a support line if you have questions, until you trust yourself more than anyone else with the answer. Then pull the trigger. Good luck!

[nuhale]

There are many write ups on all of this on this forum. A hint to use google to "Factory Five (Ask question)" and you will find the link.

1. The KC1301 that you bought are the same fronts that come with the kit with the ~11" rotors.
2. The KC1304D kit that I recommended are FRONT ONLY and are the "COBRA" style brakes that were offered as upgrade on FOX/SN95 mustang. They fit, they work and many of us have upgraded. Look at my build thread for my MK4 build and there is a pic showing the size difference.
3. I am unsure of what FFR sends as stock rear brakes for their IRS option. I have the older IRS on my MK4 and think they are the same offered today with an adapter bracket. On my current coupe build I opted out of these brakes and bought POWER STOP S15030 calipers (stock 2015+mustang rears) with K6812 13" rotors and pads.
4. with the use of these rear calipers I bought stock Mustang 2015+ ebrake cables that required some minor modifications with removal of some brackets and shortening length and using a lokar shackle at the handle. They have a unique hook and loop style interface.

https://thefactoryfiveforum.com/attachment.php?attachmentid=152978&d=1630698904

https://thefactoryfiveforum.com/attachment.php?attachmentid=152979&d=1630698904

https://thefactoryfiveforum.com/attachment.php?attachmentid=152981&d=1630698904

[Cutter 54]

Thank you both. The 15” front rotors look great but functionally are overkill for me. I feel better about the fronts now.
I will follow up after they arrive.

[NA5KAR]

So, last Sunday, I decided that it was 'new brakes installation day'. I received my Powerstop kit and had it laid out on the table. I got the PBR drivers side caliper assembly off the car and put it next to the Powerstop caliper. They didn't look the same. It took me a couple hours to start to understand how the Powerstop caliper and bracket functioned. In my defense, there were no instructions in the box, there are no how to videos on youtube, there are no videos on the Powerstop website. To make matters worse, Chat GPT thought he was giving me a clear explanation of how the kit worked, but he also had no clue. Anyway, I figured it out, and it's a really cool setup. I made a video to help anyone trying to figure it out. This is the first video I've ever done trying to semi teach someone how to do something, so don't expect too much. Here are the things I discovered while watching it. I say the word Bracket way too much. I should never make a video again showing the profile of my face. If I do show my profile (I won't) it should be the side without the band aid. Disclaimer over. Hope the video helps. https://youtu.be/52d1OhozLcQ

[nuhale]

Nice video. Easier to install the caliper bracket to hub first then snap in the caliper and slide in the pin after. These are "floating" caliper design vs. the traditional slide pin.

[NA5KAR]

Nice video. Easier to install the caliper bracket to hub first then snap in the caliper and slide in the pin after. These are "floating" caliper design vs. the traditional slide pin.

Thanks nuhale. Now I can see it. I've done tons of brakes, but never heard of a floating caliper. It makes much more sense to install the bracket first. I couldn't see that while trying to figure out how everything goes together. The passenger side goes on today. I'll do it the right way.

[Norm B]

I found the Haynes manual for the sn95 mustang very helpful with these kind of repairs.

Norm

[GoDadGo]

I had the same issue so I simply replaced my calipers.
.O'Reilly carries that brand and I think they come with a lifetime warranty.

[Cutter 54]

Thanks for video. Worth the effort. Please follow up with rear brake upgrade, assuming you stay with Powerstop hardware. I am staying with the PBR brakes all around for the present. I got the rears to behave.