Between my 84 SE and 86 GT and an 84 SE parts car, I have had problems with 5 sticky calipers. First was the 84 SE right front. This car was low miles (55k), but had been setting for several years. The symptom was overheating. I took the caliper off of my parts car, no change. Installed a caliper kit in it, no change. Then I replaced the brake hose, seemed better, but still over heats (although not as badly). Then the left front started overheating. I put in a caliper kit, new piston, and brake hose. Still overheats. I gave up on the left front and put on a Bendix rebuilt caliper and it works fine now. In both cases, the piston bore looked like it was brand new. I cleaned the crud off with Chemtool, washed them in soap and water, blew them dry with compressed air, and reassembled them with clean DOT3 brake fluid as a lubricant. I test fit the pistons in the bores before putting the new seals in, and they seemed a little tighter than I would have expected. The caliper bolts were clean, and I lightly greased the sleeve when I put them back together.

What is going on?!! Now the right rear has started overheating as well, and my 86 GT right front...same thing. Am I just lucky or is this a common problem? Do piston bores get smaller with time? Or do the pistons grow?

Generally, I'm willing to spend more $ in parts to rebuild something myself in order to avoid aftermarket rebuilt parts(often poor quality), especially when my cores appear to be in good condition. No car has whipped me yet, help!

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Three and counting...
2m8 in process

Did you check the pads? Many come with so much paint on them that they bind in the caliper and don't retract. I've had to take a grinder to all of them to get them free. Also, when you put the caliper back on, there's a machined groove on the knuckle that the whole thing slides on. That needs to be greased as well as the slider pins. Try the caliper with the pads out. It should slide freely.

ive heard rumors (dont know if true) that over time the phenolic pistons swell up a tiny bit and just never work right. ive had very poor luck with rebuilding calipers and just let the pros do it now.

Are you are using Chemsolv to clean the brake parts? If so and the pistons are phenolic, they might expand. That would explain the tight fit you described. If you have steel pistons, disregard this.

quote Originally posted by Gary W: Did you check the pads? Many come with so much paint on them that they bind in the caliper and don't retract. I've had to take a grinder to all of them to get them free. Also, when you put the caliper back on, there's a machined groove on the knuckle that the whole thing slides on. That needs to be greased as well as the slider pins. Try the caliper with the pads out. It should slide freely.

Good suggestion Gary, I'll give it a try.

quote Originally posted by lurker: ive heard rumors (dont know if true) that over time the phenolic pistons swell up a tiny bit and just never work right. ive had very poor luck with rebuilding calipers and just let the pros do it now.

That's what I'm wondering lurker... Older systems would definitely have water in them.

quote Originally posted by spark1: Are you are using Chemsolv to clean the brake parts? If so and the pistons are phenolic, they might expand. That would explain the tight fit you described. If you have steel pistons, disregard this.

Spark1, I cleaned the metal parts that way, but not the piston (which is phenolic), and I replaced one piston with a new one (also phenolic).

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Three and counting...
2m8 in process

Hmm my brakes worked great. Untill I decided to replace to front pads. Now my LF is sticking. I though I might have damaged a seal when compressing the piston so I pulled the caliper off again and worked it in and out of the bore. Put it back on and still sticks. Ill try getting rid of the paint. I hope it works but my RF works fine and they have the same pads??? I hope I dont have to shell out for a new caliper.

[This message has been edited by red85gt (edited 01-01-2004).]

After hearing (and participating) in many of these these brake horror stories, I can't help but think It would be better/easier/safer to just replace the calipers when doing a brake job. Approx $30 USD @ Autozone (each), versus what Midas, Pep Boys, Mineke would charge for a complete brake job, PLUS if you DIY with new (rebuilt) parts you know if its right or not.
On a 15+ year old car, I say if a brake part is suspect, REPLACE IT!

My $.02 worth.

quote Originally posted by NEPTUNE: just replace the calipers when doing a brake job. Approx $30 USD @ Autozone (each),

oreilly's was selling them (front calipers) for $15.99 each a month or so ago.

how much are rear calipers? i was told aroudn 400 a piece

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'86 Fiero GT


www.KylesFiero.tk

I payed $150 a piece for mine. canadian.

rear calipers 84-87 here at any napa or advanced auto parts, run $63.99 each, and front's run 27.99, give or take $5

matthew

quote Originally posted by TaurusThug: how much are rear calipers? i was told aroudn 400 a piece

i got a pair at carquest a little over a year ago for $78 each.

quote Originally posted by NEPTUNE: After hearing (and participating) in many of these these brake horror stories, I can't help but think It would be better/easier/safer to just replace the calipers when doing a brake job. Approx $30 USD @ Autozone (each), versus what Midas, Pep Boys, Mineke would charge for a complete brake job, PLUS if you DIY with new (rebuilt) parts you know if its right or not. On a 15+ year old car, I say if a brake part is suspect, REPLACE IT! My $.02 worth.

I always do my own work, and the cost of the rebuilts is not so much the issue... I worked at NAPA for several years. We had "proffessional quality" and "do-it-yourself quality." Pros won't tolerate repeated come-backs, but I guess if you do the job yourself you are supposed to expect an inferior result. I've found that "walk-in" customers are always quoted the lower-price (lower-quality) part first. Ironically,the lower price part is usually the highest profit- margin part. I still occasionally buy stuff from Advance and Auto Zone, but I ask what all of the options are. You get what you pay for.

I also left out one step. When I first started this, I bought a "rebuilt" caliper (under $20). It leaked like a sieve. The second (Bendix) rebuilt cost twice as much and seems to work fine.

My theory is: 1. If the first part lasted 100k miles, then the replacement part should last 100k miles. 2. Other than normal wear items (brake pads, etc.), I should never do the same job twice.

I guess I should just buy the better rebuilts and forget about it, but it still bugs me knowing that I should be able to get the same or better result myself. Maybe I should mic the piston and bore. Does anyone know what the correct clearance should be?

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Three and counting...
2m8 in process

Most "sticking caliper" problems aren't caused by a sticking piston - they're caused by the caliper binding on its slides. If it doesn't slide freely you'll have problems with brakes dragging / overheating.

Check the Ogre's Cave for details on how this should be done correctly; clean the corrosion off of the slides on the knuckle and lube it (and the slide pin bearings) with the right grease and your problems will go away.

I guess I’ll throw in my thoughts.
Most calipers I’ve rebuilt I find a large amount of what I believe to be calcium build up in the groove for the piston seal.
In fact I have a little tool that I made about 15 years ago that I still use for cleaning that groove.

So the grove in effect is smaller with the build up inside there, making the seal squeeze around the piston tighter.

"Sticking pistons" amount to one of three things.....

The piston is actually sticking. This means either the seal is binding or the caliper bore has crud in it. Either means the caliper must come apart.

The lines are blocked. They can be blocked anywhere between the MC and caliper/slave cyl. Bad rubber lines and bad combi valves are common causes.

MC or brake booster is bad or misadjusted. If the MC pistons don't return to full rest then they can hold pressure in the lines. Worse as the fluid heats, line pressure will increase due to fluid expansion. That means the caliper will not just have release problems but can actually bind tighter as things get hot.

Since at least one person above had this happen after a "brake job"... I would tend to lean toward crap in the caliper binding the piston.

Yes, replacing calipers durring a brake job is a good idea. Especially the rear calipers. HOWEVER... You have to buy good calipers. Especially the rear calipers.

Cheap rebuilt rears very likely are reusing pistons or using off shore pistons. There are parts in the pistons that go bad and the pistons really have to be replaced to get a good caliper.

Fronts are more forgiving. There are a few rubber parts that get replaced and maybe a new piston. (piston depends on condition and the rebuilder...) Still, Rebuilding the front caliper isn't quite as easy as a quick hone and stuffing new seals. If the groove where the main seal goes gets botched up you will have problems with the caliper. Leaking is the most obvious problem but it's not the only one. The actual shape of that groove is important to reliable caliper operation.

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Be alert. The world needs more lerts...

The Ogre's Fiero Cave (It's also at the top of every forum page...)

What frustrates me is. A If I remove the caliper and press the pedal to extend the piston I can push it back in with a C clamp. B The hose isent at fault because if I pres the brake then unscrew the bleed screw it makes no change. Theoretically this should relieve the pressure and allow the piston to relax. C I buffed off my slides and lubed with brake silicone grease. So I really hope its just something making the pads bind. The RF works fine and all the front brake parts are the same age. Hmmm I am going to try swapping pads left to right and see if anything changes. I am going to do the Zettner upgrade sometime in the future just wish I dident have to spend money on these old crappy brakes dam inspection.

[This message has been edited by red85gt (edited 01-02-2004).]

Thanks guys, this gives me a lot more ideas. I'm going to right front another try using all of this info.

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Three and counting...
2m8 in process

I fought that battle for quite some time in the summer time and it turned out that both front callipers were warped and binded when they slid back and forth..Upon replacement of the callipers the problem was solved. Good luck

quote Originally posted by red85gt: What frustrates me is. Etc....

You have bad caliper(s). Changing pads won't help.

They are pretty old by my guess. I wish I could upgrade instead. Ill be buying new ones in spring.

[This message has been edited by red85gt (edited 01-03-2004).]