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Rebuilding brake calipers


rich_e777

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So Ive got the calipers off the 1995 and one of the boots is torn on a front caliper.  Plus they are old, dirty and a bit rusty but perfect for some paint. I do not have an air compressor yet nor can I find a fitting for my grease gun that will thread into the caliper in order to pop the pistons out. I know the rears just thread out but for the fronts is there any way to get the pistons out without using the compressed air or grease?

 

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I meant to get the piston completely out of the caliper to replace the dust boot. Manuals say to use compressed air until they shoot out and I read a grease gun could be used in a similar way.

 

I'm going to do the same thing for the 1994 when the time comes.

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i would think the residual grease would probably be a pain to completely remove if you went that way. I've never rebuilt calipers, but I assume the brake fluid is all of the lubrication the piston/seal needs, a petroleum grease may compromise the seals.

 

if you can't hack something together with compressed air, I like the re-using the master cylinder idea.

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Well I tried using the bleeder valve and grease gun, that won't work. Using the master cylinder will expand the piston but won't pop them out. Since a boot was already ripped I dug what I could out after compressing the piston and like heartbeat said they pull right out. So it's easy getting apart just remove what you can of the boot. Got everything soaking in concentrated Zep now.

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I use compressed air, unless the piston is seized.

 

With compressed air, you'll need a piece of wood to pad the caliper housing--the piston will FLY out of the bore, and can be damaged when it hits the far side of the caliper.

 

A grease gun will move a seized piston.  Takes a bunch of grease, it's messy, it's ugly, it requires time-intensive cleanup...but I've never seen it fail to remove a seized piston.  No, you can't use the bleeder screw as a grease zerk, but you can spin a non-thread-matching grease zerk into the brake hose hole and pump away with the grease gun.  I've done this multiple times; it doesn't seem to damage the threads as long as you're threading the zerk in lightly.

 

I have seen a vice-grip sort of tool used to pull pistons out.  Never tried one.

https://www.amazon.com/OTC-4799-Piston-Removal-Locking/dp/B009S4SZ3S/ref=sr_1_1?ie=UTF8&qid=1471729545&sr=8-1

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(Well I went to add to my last post and the text disappeared..so..)

 

A bicycle pump should work as some go over 100 psi. Easier with a floor model?

And it may clamp directly onto the bleeder valve, or require a little tape or rubber to build diameter.

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Honestly Imp that's what I`m sort of doing now. Got lots of pics in a word Doc. and will try and format everything tonight after work.

 

I searched about 4 different places yesterday and couldn't find the part with the correct thread size to use on y grease gun so figured I`d at least give the bleeder valve a try. It worked In filling the caliper up with grease wonderfully but the grease gun fitting wouldn't hold tight enough to expand the pistons.

 

The pistons can be removed without any special tools and without damaging the boot I found, compress them all the way in then grab them with channel locks, vice grips etc and yank them out. Its hard to pull them out extended but far easier to pull them compressed due to the way they hold pressure on the seal in the extended position.

 

Now the dust boots are going to be the pain in the project if you have to replace them, they like to melt to the metal and that has to be scraped off. Like a timing cover gasket only in a small hard to get at tapered hole. A few hours with a pick and razor blade does it pretty good, then I`d recommend a wire brush or sandpaper to get the piston seal and boot area on the caliper clean. I also took some metal polish to the pistons and cleaned them up good so everything goes back together easier.

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Well I tried using the bleeder valve and grease gun, that won't work. Using the master cylinder will expand the piston but won't pop them out. Since a boot was already ripped I dug what I could out after compressing the piston and like heartbeat said they pull right out. So it's easy getting apart just remove what you can of the boot. Got everything soaking in concentrated Zep now.

 

Run the engine and it will pop off. I had a brake emergency when my T60 bolt shot off and the piston actually shot out. It can be done that way.

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One of the first time I ever did brakes was on my dad's old Pontiac 6000. I stepped on the brakes to unlock the steering wheel and straighten the wheels out and blasted a piston right out of a caliper. that was right up there with the time I took a ball joint apart and the spring unloaded and ripped the CV shaft apart and threw the balls all over the ground. not exactly my finest moments in auto mechanics

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Well finally got around to fooling around with these things. Figured I should put them back together before painting them, 6 hours and 3 seal/boots later both front calipers ended up as cores for new ones. I tried several different ways to get the boots in but I ruined all but one. For $60 I`ll let those old calipers be Mexico's problem now.

 

IMHO now its not even worth it to rebuild these unless you are doing it for :shrug:  fun, IIRC I`ve seen them as cheap as $25 on rockauto and its worth it to avoid this headache.

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Well finally got around to fooling around with these things. Figured I should put them back together before painting them, 6 hours and 3 seal/boots later both front calipers ended up as cores for new ones. I tried several different ways to get the boots in but I ruined all but one. For $60 I`ll let those old calipers be Mexico's problem now.

 

IMHO now its not even worth it to rebuild these unless you are doing it for :shrug:  fun, IIRC I`ve seen them as cheap as $25 on rockauto and its worth it to avoid this headache.

 

When my piston shot out in the middle of the month, I thought it was a simple push back in ordeal. Well when I found the piston, it was anything but. Played around with it for 5 minutes and said "fuck it" "i'll get a reman caliper tomorrow at Advance Auto Parts." With speed perks and a 30% off coupon, I paid...

 

 

$25.

 

With ceramic pads, brake fluid and taxes, I paid....

 

 

$60.

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That's the Pioneer spirit at it's finest right there!

Had I kept that expedition up it would have cost me more in rebuild kits than a caliper would have anyways, plus time which isn't cheap either. Also the new ones were clean and ready to prime after a squirt of brake cleaner. The old ones really needed blasting or hours of wire brush work.

 

 

What did you need a copy of?

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...And just out of curiosity, to the folks that actually have rebuilt a front caliper. What method did you use to get the dust boot/seal back in? Not the squared O-ring piston seal but the larger dust boot seal.

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...And just out of curiosity, to the folks that actually have rebuilt a front caliper. What method did you use to get the dust boot/seal back in? Not the squared O-ring piston seal but the larger dust boot seal.

I haven't done this on my Luminas, but in general the dust seal is installed into the caliper, then the piston is pushed in while blowing compressed air into the hole that takes the banjo bolt.  You only need enough air volume to "inflate" the seal over the piston.  The piston will only go in the caliper to the square-cut seal, then you remove the air pressure to push the piston past the square-cut seal and in the rest of the way.  The square-cut seal better be lubed with brake fluid or specific brake seal lubricant before you try to install the piston.

 

If I think of it tomorrow, I'll check the service manual for the specific procedure for a '92.

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I could never get the dust seal to seat into the piston bore without damaging the seal itself. I`m also pretty sure I damaged one caliper trying to scrape off the baked on rubber as well which was another reason to just get new ones. The rear calipers may be different but after dealing with the front ones I`m just going to clean them up real good and paint them like the front ones as long as the piston boots look good.

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