Caliper Rebuild Help

[Gumart1]

I decided to rebuild my calipers because I had one piston that wouldn't release. I followed the tutorial on Lexls and used compressed air on my front dual caliper but only 1 caliper came out. I tried pliers, and also tried replacing the loose caliper and holding it in place with wood and using air again to release the other. I had the compressor up to 90psi! It still will not budge.

Any suggestions other than buying a new caliper?

[SRK]

Air is extremely dangerous for removing caliper pistons. The real way is to hydraulic them out before disconnecting the fluid line. Pop the removed piston back in, bleed the brakes to that caliper, and then use a block of wood to retain the piston that moves (or the old pads) and then remove the stuck piston by slowly pumping the brakes. You can even start the engine to get the booster working if you like. Unlike air, when the piston does finally come out, it will just quietly fall out, and not come out "explosively" like compressed air does. And as you have noticed, 90 psi is nothing to a caliper - they normally operate at hundreds of psi, and will see 1500 psi on a panic stop. So jack it out hydraulically.

[Gumart1]

Thanks SRK, but, the piston was stuck before I removed the caliper, so pumping the brakes would do nothing to release it. Plus, when the other piston that is not stuck is removed, it leaves an opening that was normally blocked by that piston which would have forced the fluid into the other (stuck) piston. With the one good piston out I have no pressure for fluid or air.

If what you are saying about fluid psi vs. air psi is true, why isn't that the standard method of piston removal? When I do a google search for caliper rebuild, every tutorial uses the air method.

[jeffls400]

Hi - Had the same issue when rebuilding my calipers last fall. Place the non-stuck piston back in its bore, and fabricate a piece of wood that does not allow this piston to move in its bore at all when the air is applied through the port. Make sure the bleeder valve is completely closed, and try again to release the piston, slowly increasing the regulated pressure until the stubborn piston pops out. Just make sure you have a piece of wood in place to keep this piston controlled when it does break loose. It only took a couple of tries to release mine, and I would estimate the pressure was about 100 psi.

Jeff

[Gumart1]

Hey Jeff, I'm going to try just that again. My compressor air gun has a 90psi max, and the air was trying to escape in every possible place, but I'm also going to try to lubricate the bore of the stuck piston the best I can first. Will let you know if it works. Thanks

[SRK]

Perhaps you could read my post a little more carefully. I advised to re-install the removed piston, bleed, block it, and pump the brakes. If 1000 psi won't move the piston, 90psi of air won't budge it. Then you'll require a new caliper, or at least a new piston, as rust will jam them.

I am not concerned with most of what's written on the internet.

[jeffls400]

Using compressed air is the Toyota recommended method. However, if the piston will not budge, it is definitely possible that you may be better off exchanging for a rebuilt / remanufactured caliper.

[Gumart1]

It worked. I reinstalled the good piston and blocked it and with lots of air pressure and patience the other finally came out. Unfortunately, the bad piston has some pitting and rust which will not come off so it looks like I am in for a replacement. I cleaned and lubed the piston and it did go back in smoothly, but who knows how long it will last and I'd rather not chance it with my new rotors and pads.

[SKperformance]

After rebuilding all of my calipers this weekend , i can tell you if it is pitted then buy a replacement as the piston cylinder walls as well as the piston.

It might be cheaper to get a rebuilt caliper with new inner and outer seals then 2 new pistons usually around 60.

I would never use compressed air as the hydralic pressure is more than enough but is such low volume it causes no issue.

i read it in my manuals as well to use air but i don;t know any tech who does it that way beside a rebuilder .