945LSTANG

i've been having issues with my rear driver side brake recently and decided i would start taking things apart today after class. in the process of disassembling the caliper i found this:






these score marks do not go around the entire circumference of the piston. they cover around 2/3s of it. any ideas what could've caused this and what i should do? the piston bore appears to be clean and I can't see any signs of wear. here's a pic of the bore:



i realize you can't really see much in this pic, but maybe some of the more experienced members will see something that i don't. i can take better pics if need be. i also realized that i haven't finished disassembly. I just wanted to pause and get some opinions on the piston. thanks in advance for any advice that you guys give!


Rob

pete1665

the only thing i can think of is that the caliper slide bushings (through which the cailper bolts thread) are notorious for rusting and seizing. If that happened to one or both of the bushings then I could see the potential for damage when the piston tries to slide and return.

Regardless of how it happened though, I would say just replace the caliper(rather both rear calipers). They are cheap enough...I believe around $30-$40 for stock calilpers last time I checked.

945LSTANG

you have a link? and are you sure they are the cobra brakes?

i've got the parts to rebuild it if need be.

pete1665

ahh, didnt notice you were a cobra. Is there any rust on the caliper bolts or in the bolt holes on the caliper mounting bracket?

http://shop.advanceautoparts.com/web...|GRPBRHYAMS___

945LSTANG

negative....no rust.

those were the prices i was expecting too. i think i might just rebuild them and replace them once they are 100% shot. i already have the parts and they were only $30.

before i took them apart, everything was working fine for the most part. they were just a little noisy every once in a while.

thanks for the helping me out man!

a_penquin

The scoring may have happened due to some dirt that became lodged in between the seal and piston. Ive seen it a lot and most of the time its not an issue unless its leaking. If you have the rebuild kit, clean everything thoroughly and inspect the caliper bore for signs of damage and wear. If everything is ok, rebuild it, otherwise buy new (or refurbished) and use the old as core.

945LSTANG

yeah i already cleaned/flushed the inside of the bore with brake fluid. the funny thing is is that there are no signs of wear on the boar itself. im going to rebuild it today and see how it turns out. worst comes to worst, i can replace them further down the road when they are guaranteed to be shot. thanks for the response.