best way to get brake calipers unseized

I have a set of narrow glide dual discs and both the pistons in the calipers are seized i used a vice to compress them about 1/8 inch. i let them soak in wd 40 for a day then used an air compressor to try and blow the piston out but no such luck. any ideas

Originally Posted by Trevor04

I have a set of narrow glide dual discs and both the pistons in the calipers are seized i used a vice to compress them about 1/8 inch. i let them soak in wd 40 for a day then used an air compressor to try and blow the piston out but no such luck. any ideas

Had that happen on a T bird I owned many years ago. A buddy, who's a mechanic, completely disassembled the caliper, soaked all the parts in wd40 (I think) and it was all set. It literally took him 20 minutes. I would assume mc calipers would be no different.

i had a seized piston in a banana caliper because the rubber boot rolled up and got stuck, air wouldn't work so i put a torch to it and burned that bitch out just be careful not to hold it in one place too long or you'll melt the aluminum

Unscrew the tip of a grease gun and screw the gun into the caliper. You only have to catch a thread a tiny bit (in case the threads are different) for it to hold. Pump grease into the caliper and it will push the piston out. It's messy, but has always worked for me, even in the worst cases.

Mine were seized also. I soaked 'em in WD40 over night, then hooked the caliper up to my compressor. Gave it all the pressure my compressor could deliver. No luck either. Took a screwdriver and my hammer and GENTLY tapped on the side of the pison (not on the surface that goes donw in the caliper - just the part where the rubber seals). 2 minutes later I shot that baby up in the ceiling - still got the mark to remind me.
Went inside, changed my shorts and did it all over again with my other caliper.

Originally Posted by Stabler

Mine were seized also. I soaked 'em in WD40 over night, then hooked the caliper up to my compressor. Gave it all the pressure my compressor could deliver. No luck either. Took a screwdriver and my hammer and GENTLY tapped on the side of the pison (not on the surface that goes donw in the caliper - just the part where the rubber seals). 2 minutes later I shot that baby up in the ceiling - still got the mark to remind me.
Went inside, changed my shorts and did it all over again with my other caliper.

I did one of mine the same way only the piston shot across the garage, through the window and into the front yard!

Did u just use an air gun or did u have some fitting that u could screw it in to the compressor. And after it shoots out do u have to replace any parts or can u just put it back together

Grease gun is the safest and will clean out the bore while whipping all the grease out. Just slip the grease gun over the bleeder after you loosen it of course and pump the piston out.

How do u get all the grease out that u pump in there

Originally Posted by Trevor04

Did u just use an air gun or did u have some fitting that u could screw it in to the compressor. And after it shoots out do u have to replace any parts or can u just put it back together

I had an fitting with the same thread as the caliper to my compressor. If you were to use an air gun it would basically be the same as using your hand to push the piston out. You would need to press the nossle of the air gun harder in to the caliper then the pressure created by the compressor. Path of least resistance and all that..

My rubber boots were cracked to begin with so I couldn't say if they would survive this procedure. I also had my caliper clampt down in my vice at the time. Although I wouldn't recommend the method I used. You could easily kill yourself this way. At least wrap it all up in a large towel or something to absorb the power released when the piston shoots off.

Good luck and keep your head back if using a vice.

Originally Posted by Trevor04

How do u get all the grease out that u pump in there

Dig it out with your fingers and then use carb cleaner, brake cleaner, gasoline or whatever. Believe me, if that piston is frozen you are going to have to scrape out the dried brake fluid that will surely be inside and under the piston seal. BTW, I've used my air compressor too but those pistons pop out at bullet speed and can do some big hurt.