rear brake caliper

William K Denton wkdenton at
Wed Jul 23 16:43:16 PDT 2008


You can just rebuild the caliper, as long as there's not any significant 
corrosion of the aluminum inside the bore of the caliper.  If the bore is 
badly corroded the caliper is junk.  The pistons "may" need to be replaced, 
depending on the level of corrosion present, but usually clean up OK.

To remove the pistons, take the caliper to the bench, wrap it with a towel, 
face the pistons away from your body and apply compressed air to the brake 
line inlet.  Make sure you wear eye protection so you don't get hydraulic 
fluid in the orbs.  Try 40# of pressure first, but you may have to up the 
pressure depending on how gummed up the pistons are.  The trickiest part of 
this entire operation is getting the "second" piston out of it's bore.  Once 
the first one pops, clean it up a bit and press it back in far enough to 
hold pressure, then wedge a small square of plywood (or something else 
softer than the metal of the piston) under that piston only.  Then, apply 
air pressure again to get the second one to pop out.  Once the second one 
pops out you should be able to manually remove the first one again.

Scrub the pistons with hot soapy water and a non-metallic scrubbing pad (or 
toothbrush), dry and inspect for pitting or wear.  You may have to apply a 
little "persuasion" to remove some stubborn deposits, just do it with 
something softer than the chrome surface of the piston and you'll be OK.  If 
they clean up and look good, polish them with a little Mothers mag polish 
and reuse, saving yourself ~$50 in new pistons.

The rest of the caliper assembly can also be cleaned up using hot soapy 
water and a toothbrush as well.  One exception is cleaning in the groove 
where the seal goes, there you're probably going to have to resort to dental 
pick work.  Work slowly and carefully, doing you best impression of a dental 
hygienist scraping plaque off your teeth w/o drawing blood <g>.  Those 
deposits of aged, polymerized brake fluid are generally tough and non 
soluble in anything you throw at it, which is why I clean them this way. 
Other than that, the nice thing about working on brakes is that brake fluid 
(aka mixed glycols) is water soluble so it's easy to clean them using plain 
hot soapy water, which precludes the necessity of using solvents, parts 
cleaners, etc.

 Good luck!

Bill in Yardley, PA
wkdenton at
'96 GPz1100
'86 SRX600
'81 VX920RH
'80 CB-X

----- Original Message ----- 
From: "Bill Magitz" <corbie at>

This is a question regarding the 1984 Sabre my brother gave me. He said the 
rear brakes were sticking , but when I removed the caliper I found the 
pistons to be frozen in place with corrosion on the exposed sections. Now I 
am not even a good shade tree mechanic so i am not sure what my best option 
here is. Do I try to free it and clean it up or do I just replace the unit ? 
If I try to free it what would be a good method , I have an ultra sonic 
cleaner at work I can use if that helps. thanks for any advice---bill m----

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