Rear Brake Caliper Rebuild Redo

[79spider124]

I spent a good portion of yesterday rebuilding the rear brake calipers following the instructions on Mirafiori.com (http://www.mirafiori.com/faq/content/re ... lipers.htm ). Today when I gave it a test ride the rear brakes got very hot and even smoked a little. I jacked the car up again by the rear axle and the calipers seem to be completely frozen. I thought I followed the instructions well and I made sure all the parts went back as they came out.

I did notice that when I pumped the ebrake arm the piston would extend and not retract. I had to push it back down. I thought maybe this was due to not having brake fluid and pressure on the caliper yet.

I've loosened the ebrake cable and that hasn't relieved the pressure.

Any thoughts as to where I may have gone wrong? Thanks in advance for any comments.

[manoa matt]

There is a threaded rod that the piston screws onto. At the other end of the rod is a small wedge and the emergency brake actuating arm. There is a proper orientation for the threaded rod in relation to the actuating arm. One side of the rod has a higher "tang" than the other side. If its reversed it can bind. The mirafiori article does not give a clear photo of the orientation, but the second to last photo will give you an indication.

Another possibility is air in the system. There is a line scribed into the face of the piston that must be oriented properly to bleed the calipers. With the caliper in the normal position the line will be horizontal and on top. You will also need to unhook the torsion bar on the rear brake equalizer at the axle and push the bar up and support it to open the valve so the rear brakes can be bleed.

[narfire]

Further to Matts coments, the rubber seal/ring could have been nicked and a chunk of rubber has "jambed" preventing the piston to retract. A piece of dirt would do the same. ( had the same issue with my front brake)

[manoa matt]

Got to be brake fluid in there for the piston to retract, even with all the mechanicals of the emergency brake.

[spider2081]

Any chance the hose to the caliper is restricted?? I had the center hose partially clogged. It let the fluid under pressure go to the calipers but did not let it out.

[79spider124]

I started over and took each caliper completely apart and rebuilt again. I'm certain they we done correctly the 1st time and just as certain I did it correctly the 2nd. However, I experienced the same problem. After bleeding the brakes, the calipers would seize. But I found that if I pumped the hand brake they would release some. Then if I step on the pedal they freeze again. I played with the compensator but to no avail.

So I made a huge mistake and decided to drive it around to see if they just need to be worked out.

Disaster!!!

I started smelling the hot brakes. But before I pulled into the driveway the brake hose actually exploded from the heat and shot fluid everywhere causing a huge white ball of acrid smoke. Then the Fiat emblem on the whell melted off. I doused it with a bucket of water to cool everything off. My simple rebuild just turned into a major project.

And I still don't know what the problem is. Plan of action...new calipers to start.

[So Cal Mark]

I'd plan on replacing the brake hoses. Since hindsight is so perfect, you should have opened the bleeders with the calipers stuck to see if there was pressure. You may also find the axle seal is damaged if the wheel was that hot

[kmac33]

Rick,
In addition to Mark's recommendations, I'd consider bypassing the rear brake compensator. Feel free to contact me if you ever need an extra set of hands for any repair project, I'd be more than happy to help. (I'm in Stone Mountain/Lilburn)
404-291-3789

[manoa matt]

Yes, replace all brake hoses (every 4 years) and replace the compensator, do not eliminate it. The Fiat engineers put it there for a very important reason.

[79spider124]

I have purchased rebuilt calipers, hoses and brake pads and will start over this weekend. Now that I've pulled the calipers off 3 times in the last week, I should be able to knock it fairly quickly. I did not purchase a new compensator. I'm hoping that the calipers were the source of the problem. Certainly, the compensator is my next plan of attack if things don't resolve with the new calipers and hoses.

Thanks for the offer, Kevin. I hope to meet up with you and all the other North Georgia owners for a Spring drive in the hills soon.

[79spider124]

Last night I completed the job of installing factory rebuilt calipers, new hoses and new pads. Fortunately there did not appear to be any damage to any other parts from the overheat and subsequent water douse.

But unfortunately the problem remains. I have not reattached the hand brake cable. When I press the pedal, the rear brakes lock up. The only way to relieve the pressure is to open the bleeder valve.

I have not touched the compensator and the brakes were actually working fine prior to me wanting to fix the hand brake. Could it be that by bleeding the brakes I have damaged the compensator. Should that be my next plan of attack? I have read that this is quite difficult and there seem to be differing opinions as to whether it should just be bypassed altogether (although I personally would be hesitant to do so).

All thoughts would be appreciated as I am certainly perplexed.

[digitech]

Sounds to me like the compensator is trapping pressure - I'd install a new one, certainly not hard to do, assuming the nuts aren't rounded off. If you place jackstands under the axel and lower the car onto them, you won't have any problem bleeding the brakes.

[79spider124]

I finally had an opportunity to dig back into the situation yesterday. I started with the rear center flex hose just forward of the compensator. As soon as I removed one end of the hose, the brakes released. I put in the new hose, bled the brakes and sure enough everything seems to be back in working order. I didn't even have to touch the compensator. Could it be that this little length of hose (which looks from the outside to be in good condition) was the source of my problems? I'm skeptical, but I can't complain as things appear to be operational.

[digitech]

Certainly, a fluid restriction is a fluid restriction.