Now I've gone and done it... So stupid!!

[chipperwerks]

I am rebuilding my '76 brake calipers and 2 of the pistons were seized in their bores. I gave them a bath in brake fluid then penetrating oil, then deceided to get a bit physical with them. I tapped at the piston side to side and pop!! Out it went...1 more to go. Tap, tap, snap!!! The lip that holds the boot shattered and is gone..... Any ideas or is this caliper done. Could I concievably get the piston out, get a used piston and be back in business?

P.S. Anyone have an old set of calipers that I can rebuild?

[jerry]

been there, done that. you'll have to find another piston. i don't know if they are available separately. they are cast iron and relatively brittle. i just disassembled and clean one i got off this board a month ago. they show up from time to time. when the piston is not too siezed i have been able to coax them out carefully by using two opposing large screwdrivers to leverage them out.

if you have an air compressor you can try to blow them out by pressurizing the inlet. put a piece of wood between the pistons to prevent unintended projectile. it can be frightening to the uninitiated if it all of a sudden lets-go.

i've been toying with the idea of making a grooved fork-like tool to slide into the groove and give me something to tap them out with.

keep your eye out for a used set. they come up occasionally.

[Guest Anonymous]

I've got used ones. wbredehoft (at)gmail.com

[viali8]

seems like good price...good luck

http://www.fap99.com/ShopByVehicle.epc?q=1976-BMW---00--/--L4--1990cc--.0l--Gas--Carb--1--1-Brake--Components--Wheels&yearid=1976%40%401976&makeid=BMW%40%40BMW%40%40X&engineid=1010822%40%402002++%2F+L4-1990cc+2.0L+GAS+CARB++121%40%402002&catid=Brake+Components+%26+Wheels%40%40Brake+Components+%26+Wheels&subcatid=Front+Caliper%2C+Rebuilt@@Front+Caliper%2C+Rebuilt&mode=PA

[Guest Anonymous]

For the really stubborn ones, i've found if you crack it loose by pushing the piston in first, then use compressed air. If the air does not work, rap in the caliper with a hammer while you apply the air pressure. I know it's a little late, but this might help if you end up getting another used caliper to replace your damaged one. good luck!

[chipperwerks]

Well thanks go out to all with good advice, links, and the possibility of 2 new(to me) calipers ... Thanks Bill for taking the time to dig through your garage:). I have done all the tips and tricks suggested.... This piston is the bottom outside when on the car.... Pretty sure it is plain old rotten with rust... Therefore, Time to replace!

[scoyote]

I just went thru boxes of seized-rusted old calipers from years of dismantles. I tried air and couldn't move more than one total after the clamping off process. I resorted to fitting a grease nipple into the fluid lines and again with blanking plates --i managed to hydraulic the pistons out. Much too messy--then a thorogh solvent soak to rid the grease --then boil them to rid the solvent---crazy! I had one caliper with a broken cast ear to mount to the strut---i pushed out a piston and noticed the small bump in the bottom center of the bore--it has a small centering detent. I then drilled 1/4" thru to the outside of the caliper. Then i made an accurate template of the outside and the drilled centering hole. I was now able to drill thru to the bottom of the seized piston and with a narrow flattened punch--was able to tap the piston out easily---even some that you would swear were welded in. This takes no time to neatly remove the pistons--flip out the square "o"rings and get at cleaning things up with emery or scotch guard pads--i imagine a nice little 1" cylinder hone could be ideal if you could find one that small. Using a pbr assembly lube--not brake fluid--you can refit your rings and polished stainless pistons into their glistening bores (aim high here!) so they slide in with finger pressure. I then tapped for 5/16" and used 300 degree loctite and a small allen head grub screw to seal things. I really can't see a down side---calipers don't leak and they are now serviceable! If you play around with prying the cast hats or using vice grips--you're asking for trouble and most times will ruin your cast tops and dust boot lands. I'm sure i'll get some comments --on this fix ---but i'm going to try them on my car first!----scoyote

[Bimjam02]

haha i just did the same exact thing 2 days ago...