Rebuilding Brake calipers

17875 Views 32 Replies 18 Participants Last post by Peter, Dec 23, 2017

Peter

Discussion Starter · Aug 21, 2007

Folks, it's that time again that I come to you for some guidance. When backing out of the garage the other day, I heard one of the rear brakes of the GTV drag a little. So I decided to take a look. Based on what I saw with that one caliper, I decided it's probably time to rebuild all four...here's some pictures. It looked like many of the 8 pistons were likely stuck, looking at the rust. Some of it was hidden behind the dust cap....the top piston in the last picture was actually the one making the rear brakes drag..... I was surprised this car had any stopping power at all

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Peter

Discussion Starter · #2 · Aug 21, 2007 (Edited)

So next thing was to get the pistons out. I searched on this forum, and there were three ways described. One was using an air compressor (potentially volatile) and the other using a grease gun (messy, and I thought it would be hard to get the grease out, as I intend not to split the calipers) or using hydraulic pressure. Well, as all four are off the car, and I do not have a spare master cylinder, I guess the last option is out....I do not own a compressor either.....So I took them to a local brake shop. They got 3 out of 8 out, with air.
So now I am trying to soak them in penetrating oil for a few days, and we'll see if they come out then (the guy said he used 90lbs of pressure, which seems like an awful lot to me, and should do the trick). If you have any other ideas on getting the other ones out, please shout.

Now, of the ones that did come out, the bores look very good, at least below the rubber seal...there is obviously rust above it, but that should not be a big deal, I would think. What concerns me is that there is pitting on the pistons....right at the top where it probably sits in the seal when the brakes are not in use, unless the brake pads are very worn

Does this cause an issue, you think? Please see the pics, I hope they are clear enough. Also, in the last pic you can see the inside of the rear brake piston. the part in the middle has quite a bit of play, is that normal???

Sorry for my ignorance, this is my first time attacking a brake job. I want to learn this stuff, instead of just buying remanufactured calipers.

Thanks for any and all advice you can give!!!

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ntj

· #3 · Aug 25, 2007

Hi,

I wouldn't go putting those back in like that - the pitting could spread down causing them to seize - then you have to rebuild them again. I'd check out getting them machined and hard-chromed, or just get new ones.

Trav

· #4 · Aug 25, 2007

White Post Restorations in White Post Virginia can rebuild your calipers.
They do beautiful work.

Joseph M.

· #5 · Aug 25, 2007

Peter,

If the pistons still do not come out, you can try the following.

Position the calipers with one piston outer face (ie face mating the brake pads) facing upwards and pour some good quality liquid rust remover between the piston edge and the bore and leave overnight. The rust remover will solve the rust at the edges, which is causing the problems. Afterwards wash it away and pour some penetrating oil and leave this soaking for a while. Then apply pressurized air (mine took about 5 bar before giving away).

Once one piston is out, you have to invent a covering plate with a rubber gasket to cover the bore hole (use a grip to press it tight) so that you can work on and press out the opposite caliper.

This is the only manner I finally managed, just soaking in penetrating oil will just not work if the pistons are badly stuck. You need to solve the rust first. The method outlined above will work, at least it did with mine, and with all the pistons.

Good luck.

Joseph

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GuerrillaGarage

· #6 · Aug 25, 2007

To tell you the truth those don't look bad at all. I went through the same thing last spring, and I live in "Upstate" New York where we know a thing or two about rust. I couldn't get the pistons out of mine either and I finally resorted to putting them back on the car without pads and casually bleeding the lines a bit and then pumping the pedal hard to get the pistons out. Clean the piston and bore of the side that comes out first and put it all back together with a pad on that side and do it all again to get the piston on the other side of the caliper free. Compressed air will easily pop the first one you this time. I used a die grinder with a little wire wheel to clean the crud out of the bores. I cleaned the pistons up on a wire wheel on a bench grinder. Clean everything really nice, and do the final assembly with a liberal application of silicone paste. Mine work great. -Steve

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Peter

Discussion Starter · #7 · Aug 25, 2007

ntj said:
Hi,

I wouldn't go putting those back in like that - the pitting could spread down causing them to seize - then you have to rebuild them again. I'd check out getting them machined and hard-chromed, or just get new ones.

getting them machined and hard-chromed, wouldn't it be hard to get to the exact same size? New one are unobtanium I think?

Peter

Discussion Starter · #8 · Aug 25, 2007

Joseph M. said:
Peter,

Position the calipers with one piston outer face (ie face mating the brake pads) facing upwards and pour some good quality liquid rust remover between the piston edge and the bore and leave overnight. The rust remover will solve the rust at the edges, which is causing the problems. Afterwards wash it away and pour some penetrating oil and leave this soaking for a while.

Joseph

I have done this....but I used PB blaster for rust removal....is that not good?

rogerspeed

· #9 · Aug 25, 2007

Now that everything is clean, they'll be fine with a rebuild kit for at least ten years. Make sure the pin holes in the pads have round shoulders, it makes a difference

AllthingsZagato

· #10 · Aug 25, 2007

Having them m/c and then hard chrome plated is no problem. As long as you have access to a decent m/c shop and have discussed with the platers how much plating allowance you need to allow for. Long term this is the next best thing to SS pistons.

gattia86

· #11 · Aug 26, 2007

0-rings for ATE calipers?

On the topic of caliper rebuilds...

I've in the middle of rebuilding my ATE calipers, and have taken them fully apart.
I'd like to assemble them with new o-rings between the caliper halves. These are some special-sized, square-edged o-rings. Does anyone know where I can get them new?

I know they're available *somewhere*, since remanufactured calipers come with them.

Thanks,
George

'74 GTV

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Joseph M.

· #12 · Aug 27, 2007

Peter,
I'm not familiar with PB rust blaster, is this in liquid form??

Peter

Discussion Starter · #13 · Aug 27, 2007

yes, here it is:

http://www.pbblaster.com/store/moreinfo.cfm?Product_ID=1

axeman74

· #14 · Aug 28, 2007

gattia86 said:
On the topic of caliper rebuilds...

I've in the middle of rebuilding my ATE calipers, and have taken them fully apart.
I'd like to assemble them with new o-rings between the caliper halves. These are some special-sized, square-edged o-rings. Does anyone know where I can get them new?

I know they're available *somewhere*, since remanufactured calipers come with them.

Thanks,
George

'74 GTV

The only way to get the original square cut o-rings is to buy genuine ATE repair kits, if anyone still has stock of them. Otherwise find a specialist seal supplier, and ask for o-rings in the diameter required (sorry cannot remember the diameter off the top of my head), BUT you must specify that th O-rings are made from EPDM (brake fluid safe) rubber. Normal rubber o-rings will fail when exposed to brake fluid, and the caliper will leak. It is very important that you ask for the epdm material.

I have used normal EPDM o-rings in the past, and all of the brake rebuilders here in OZ that I know of use normal round o-rings to replace the original square cut o-rings. No problems doing this, but I stress that the o-rings must be made from the correct material.

Axeman74

gattia86

· #15 · Aug 28, 2007

Thanks, Axeman74 for the info.

I've heard several warnings about how I shouldn't split the calipers in half... but I don't see any other way to get a hone in there.

I was wary of regular o-rings, too, because of brake fluid and temperature compatibility... but it's good to hear I can use round-shaped ones at least. Should be easier to find locally.

George

hammer

· #16 · Aug 28, 2007

Here's some pictures of rebuilt brake calipers, I have also rebuilt mine and had no problem spliting them and have them sand blasted then powder coated also in red color but will take pictures on the week end, finding rebuilt kits for the Ate's is no problem they are available everywhere.

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Joseph M.

· #17 · Aug 28, 2007

ATE repair kits for Alfa calipers are available, they come all the way from Australia. When I nrebuilt my Spider calipers, the local Alfa dealer got them for me. Make sure to use the right silicone paste which can withstand teh high temperatures, ATE paste is also available.

By the way, why would you want to split the calipers???

Peter

Discussion Starter · #18 · Aug 28, 2007

hammer said:
Here's some pictures of rebuilt brake calipers, I have also rebuilt mine and had no problem spliting them and have them sand blasted then powder coated also in red color but will take pictures on the week end, finding rebuilt kits for the Ate's is no problem they are available everywhere.

looks really good!!!!

Peter

Discussion Starter · #19 · Sep 9, 2007

fellow Alfisti.....after weeks of soaking in PB Blaster, the remaining 5 pistons are still stuck.....This probably means that even if I were to get the pistons out, the rust is so bad that they are beyond repair. Do you think this is a correct assumption? Any other ideas getting them out?? And the million dollar question.....would they even be worth something to companies that accept them as cores???

Alfajay

· #20 · Sep 9, 2007

Nah, your's are fine. Just follow the advice that "Guerilla Garage" (sp?) posted on 8/25, clean up the rust, install rebuild kits, and go. Hydraulic pressure will exert a LOT more force than air from a compressor.

Rust on the outside of the pistons and calipers is irrelevant. Of course, the insides must be absolutely clean, and the od of the pistons has to be smooth. But, from your photos of the disassembled calipers, the insides looked OK. Dunno why the last ones are so stuck, but I wouldn't give up yet.

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