Rear caliper replaced

I'd suggest to go ahead and continue disassembling the caliper before ordering a new one. As was suggested earlier, using air pressure to pop out the piston works well. You may find it is still serviceable. If it turns out to be completely unrepairable, then I'd consider replacing both sides with new ones as a matched set.
 
I'm surprised Carl didn't chimed in to suggest to put front calipers in the rear... Maybe he was too busy running after a car going downhill because the parking brakes were removed...
 
Did disassemble the piton from the caliper. The piston was all the way out when I used the 4 ft pipe to cross thread it.
No I am not going to tap and die a caliper. To cheap to risk my car for when I do it wrong.
 
I have recovered!
Attached please find my best effort.
Nice write up on the rear caliper innards Tom. That series Belleville washer system is a hoot. I've never seen anything like that on a car. I'm curious if the pistons are stainless or just plain steel with nickel plating maybe? Was there any rust pitting or plating flaking on your pistons? Usually one can get goo and varnish off a nickel plated piston with lacquer thinner and maybe a wad of 0000 steel wool on the really tough spots.
 
Nice write up on the rear caliper innards Tom. That series Belleville washer system is a hoot. I've never seen anything like that on a car. I'm curious if the pistons are stainless or just plain steel with nickel plating maybe? Was there any rust pitting or plating flaking on your pistons? Usually one can get goo and varnish off a nickel plated piston with lacquer thinner and maybe a wad of 0000 steel wool on the really tough spots.
Thanks. When I bought the car it had no brakes at all. The master cylinder was shot. I know the car sat in a barn for 19 years. The PO had passed away and I was told that "for a while" his family would periodically start the car let it get up to temp and shut it off. As far as I know it hadn't been driven for a very long time. There was some light scoring on the pistons, and some rust pitting from moisture that had been absorbed into the old fluid. I took it slow and easy and they cleaned up nicely. The photos show what they looked like when I tore it apart, and the two on the right show how they looked after cleanup. I'm not completely sure, but it appears they are steel with nickel plating. I'm surprised there wasn't more surface degradation and flaking of the plating. New and perfect is "of course" great... but unless your pistons are "really jacked up" the outside surface doesn't have to be perfect. They just can't have anything sticking up "above the surface, that could abrade the inner surface of the seal where it makes contact with the piston, and it can't have any scratches or scores that are deep enough for brake fluid to squeeze by the seal. Seems to be a pretty forgiving design. I still can't believe the car actually stops now!
 
I've always known them as Belleville washers. Not sure where the name comes from, maybe the inventor? They can be arranged in parallel, or in series like in our calipers. Here is a link:
https://www.engineersedge.com/belleville_spring.htm

Despite the similar terminology to resisters in a circuit they behave quite differently. I've seen them in bridge and building isolation. Never on brakes!
 
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Did disassemble the piton from the caliper. The piston was all the way out when I used the 4 ft pipe to cross thread it.
Got it, I might have missed that earlier. Then definitely time for new.
Brakes are one of those areas where some are stricter than others; some feel they should only be replaced in matched pairs, while others don't. Honestly to me it would depend on the whole situation; what condition the other caliper looks to be in after tearing it apart/inspecting it, how much I drive the car and under what circumstances, etc.
 
I'm surprised Carl didn't chimed in to suggest to put front calipers in the rear... Maybe he was too busy running after a car going downhill because the parking brakes were removed...

Well, since you bring it up, I did tell Todd what to do in an email but as usual he ignored me (we have a mutual friend who damn near makes a hobby of rebuilding Fiat calipers with the rear calipers being his specialty). In any event, the 77X is pretty much done and the rat X will be going into the garage this week to get a set of front calipers installed on the rear...and also I think the steering rack bushings are gone so I'll be checking that too. Maybe I'll try to convince Courtney to make some super trick lightweight wheel chocks for me to use when parking the rat.
 
Reading through this thread made me realize as much as I love to fix things myself, rebuilding the rear calipers with the eBrake mechanisms is about on par with passing a kidney stone. I don’t know why, maybe it’s the whole “compress this while rotating that” with implements capable of generating serious puncture wounds - which I am good at :D I already have too many “well, it seemed like a good idea at the time” stories as it is...

I’d save myself the headache & but remans any day....
 
Reading through this thread made me realize as much as I love to fix things myself, rebuilding the rear calipers with the eBrake mechanisms is about on par with passing a kidney stone. I don’t know why, maybe it’s the whole “compress this while rotating that” with implements capable of generating serious puncture wounds - which I am good at :D I already have too many “well, it seemed like a good idea at the time” stories as it is...

I’d save myself the headache & but remans any day....

Someone recently asked me if I had a lot of experience working on Fiats. I said no, not really. But, all you really need to work on these, are a factory service manual, questionable mental health, spider monkey fingers, and a high tolerance for pain. So, I guess I meet all the minimum requirements.
 
Here's a tool I've used regularly on my older cars for brakes and clutches which works brilliantly (Brake Cylinder Honing Tool) View attachment 17336

I've never understood the use of this tool. When I did my brakes, it seemed that I wanted a tool to get into the groove where the seal sits, rather than this tool to clean up the bore. What do you all use to clean out the groove? It seemed to me the bore doesn't even touch anything else, but the groove you need to be clean and square so the seal doesn't leak
 
I've never understood the use of this tool.
Same principle as reboring your cylinder block, to clean up the cylinder wall linings so that a clean seal can be achieved with the piston rings, and in the case of master and slave cylinders in brakes and clutches, the rubber seals.
 
Same principle as reboring your cylinder block, to clean up the cylinder wall linings so that a clean seal can be achieved with the piston rings, and in the case of master and slave cylinders in brakes and clutches, the rubber seals.
I get the block honing; in the engine block the piston rings ride up and down touching the bore walls. In the caliper the piston moves back and forth in the seal, but doesn't touch the caliper bore. Leaking happens through rust or scratches on the piston. I imagine leaking could also happen through poor contact of seal with wall of the groove, but the condition of the bore doesn't really factor in. Still looking for something to clean up the grooves...
 
I get the block honing; in the engine block the piston rings ride up and down touching the bore walls. In the caliper the piston moves back and forth in the seal, but doesn't touch the caliper bore. Leaking happens through rust or scratches on the piston. I imagine leaking could also happen through poor contact of seal with wall of the groove, but the condition of the bore doesn't really factor in. Still looking for something to clean up the grooves...
Because the honing tool is in response to the original post about a frozen piston that won't move in and out. which is basically corrosion on the piston itself, or the walls of the cylinder, and it is usually the later. Once out, the piston is easily tidied up, and the seal and dust cover replaced, but you really need to use a honing tool as pictured to try and recover the caliper and smooth out the walls of the cylinder. Leaking is related to the cylinder wall as that is what the seal makes contact with.
Sure, there could be some corrosion in the grove in the piston in which the seal fits, and if that's stuffed, I'd just use a Dremel tool (or similar) followed up with a bit of folded 320 to finish.
Dremel.JPG
 
Here's the tool I use to turn the piston in and out.

I'm a bit more brutal, at least for the first one, and simply take out the pads, put a largish bowl under the assembly, a bit of something soft, maybe just some thick cardboard against the other side of the caliper, and just push on the brake pedal and shoot the damn thing out! Well, gently.
 
Nope, seal does not make contact with the cylinder wall of a brake caliper, just the groove and the piston. It does need to be clean without any protuberances though. The piston and the groove really need to be smooth.
 
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