From: Brett Maraldo
Date: Sat, 5 May 2001
Subject: caliper rebuild experience
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first a big thanks to all of you that responded so quickly to my
request for a rebuilt caliper. i appreciate the consideration! since ordering a caliper wasn't an option, because of the delay with shipping and because there were no calipers locally i could fine and finally, because a local place offered to rebuild mine for $175+tx i decided to give it one last go. so here is my quick tutorial on rebuilding calipers: - buy a caliper rebuild kit - leave the caliper on the car and connected to the brake lines - take out the brake pads - pump the brakes until it is difficult to pump them, don't press too hard. this will push out the pistons against the rotor. you run the risk that you won't be able to push the pistons back in enough to get the caliper off the rotor, in which case the situation is desperate. however i think with enough force, the right tools and some perseverance you will be able to loosen the grip of the caliper enough to get the caliper off - i did. it took a fairly thick screwdriver and some force. be careful not to scrape the rotor. if you can, use a thin piece of wood between the end of the screwdriver and the rotor to protect the rotor. two of my pistons were really seized but i was able to get the caliper loose. i found this method works well because the rotor is thick enough to let the pistons out far enough to go onto the next step and to prevent the pistons from popping out too far so as to relieve brake pressure. - once the caliper is free, remove the brake lines (11mm). as you work on the caliper, brake fluid will leak slowly. the best thing is to use two pointed dowels and place them in the holes of the brake fluid reservoir, from the opening, to prevent the fluid from escaping. put an oil pan under open brake lines just in of some dripping. - working with the caliper requires a lot of paper towels and it's a good idea to wear some latex or nitrile gloves. clean off the caliper - remove all the retaining rings around the outside of the rubber dust shields and the rubber shields themselves - using a good pair of vice grips, grab the end of the piston. not around the large outside diameter but around the top inset lip. you don't want to damage the piston surfaces - twist the pistons back and forth applying a outward pressure to try and pull the pistons out. you may need some force: hold the caliper so that the vice grip handle rotates up and down. use a hammer and tap the piston free to rotate back and forth. then, hold the caliper so the vice grip handle is horizontal with the piston to be removed facing down. place a piece of wood between the ground or table top and the end of the vice grip handle. now, smack the vice grips with a hammer as close to the caliper end as possible (the jaw end) to force the piston out. remove all four pistons and remember which piston holes they came from (very important). - using a small screwdriver remove the rubber ring seals inside the piston holes - clean all the piston surfaces and the surfaces of the piston holes. use steel wool on the pistons but make sure not to get steel wool bits in the piston holes (do this away from the caliper). wipe clean with a paper towel and examine the pistons for pitting, abrasions etc. if you see this kind of damage, just try and clean them up as best as you can. do not use anything that will scrap the piston surfaces. clean up the the pistons very well and dry them. clean out the piston holes. do not use steel wool because you will end up with steel wool in the holes. use a plastic scrub pad, toothbrush, etc. again clean clean clean and dry. if you have compressed air, blow out the holes. - open your piston rebuild kit which contains ring seals, dust covers and snap rings. being careful to not get contaminants (dust, dirt, debris, etc) in the piston holes, insert the ring seals. once in places, use your finger and run it around the ring pressing very hard to push and seal the ring into the indentation. press hard! you may want to coat the ring with brake fluid first. put the dust cover around the head of the piston. open all the bleeder valves. make sure everything is clean. coat the piston surface with brake fluid. as straight as you can, place the piston in the hole. keeping it straight, push it in. it may stop 1/2 when the piston hits the ring seal. use a piece of wood to push the piston straight into the caliper. you may need to bear down on it. - once in all the way, use some silicon based no-seize compound (make sure it contains NO petroleum products - if you aren't sure, don't use it - petroleum will deteriorate the rubber) and coat the inside of the dust cover with the compound. stuff it in there. this will help to resist moisture and lubricate the top of the piston. - install the snap rings around the dust cover. you may need to stretch open the ring. be careful not to over stretch. it's easier to seat the point of the ring on the inside where the two rings of adjacent pistons rings meet and then work the ring around. it's a PITA but persevere. once on make sure to press the ring firmly into place all around. - close the bleed valves - install the brake pads and caliper on the wheel - install the brake lines - bleed the caliper, top bleeder first, then outer and then inner bleed valves - to test, have someone rotate the tire fast, hit the brakes and have them check that the tire stops spinning abruptly. i love how service manuals assume you are working on new parts! my caliper probably hadn't been rebuilt in 20 years at least. the dust covers were mostly deteriorated and this caused the top of the piston and piston hole to rust. you can imagine. luckily there was little piston surface damage. but it all took a lot of force to get apart. hopefully i have given you some hints on how to apply this force. i will get around to other calipers another time. by the way, this didn't solve my problem: when i hit the brakes, the car jolts to the left. if i let go of the steering wheel and brake, the wheel quickly turn about 10-15 degrees to the left. i thought this was because my right front caliper was seized (ie. not working). however, because i had to leave the car overnight, the brake fluid drained out of the container and i probably got air in the other lines. so until i bleed those i can't be 100% sure that my repair was not effective. we'll see. brett |