40mm Caliper stuck, need to rebuild

[R80/7_Peter]

Hello, I ran into a problem while converting over to dual discs on my bike. Bought a used right side slider/caliper and the caliper is rusted tight. Can't get any movement out of the piston. Tried compressed air, no luck. Now I have it on the bench hooked up to a master cylinder trying to force it free. No luck either. 40mm ATE. I can't afford the $690 replacement cost but don't see how I can rebuild this one yet. Anyone experience this before? Maybe try soaking it overnight in something? Bit bummed out cause I was hoping to be back on the road and with improved brakes (going to the handlebar mounted MC also). Anyone wants to come by Austin,TX and fix this they can ride away with a 12 pack of Dogfish 60min IPA.

Regards,
Peter in Austin

[George Ryals]

Get everything ready to try compressed air again. Get a can of "freeze it". Warm the whole caliper up (I use a 500 watt flood light for this kind of thing. Once it is too hot to hold your finger on it freeze the aluminum piston with the freeze it and apply air pressure. Don't get your fingers in the way of the piston coming out (if this works). Hopefully the bore is not pitted so bad that it is unusable.

[Deleted User 72]

Get everything ready to try compressed air again. Get a can of "freeze it". Warm the whole caliper up (I use a 500 watt flood light for this kind of thing. Once it is too hot to hold your finger on it freeze the aluminum piston with the freeze it and apply air pressure. Don't get your fingers in the way of the piston coming out (if this works). Hopefully the bore is not pitted so bad that it is unusable.

The "aluminum" piston?

All of mine have aluminum calipers but steel or stainless steel pistons.

[R80/7_Peter]

Success. Must not have had the regulator turned up enough or that and a combination of several attempts. But it popped out, not pitted that bad, minor, enough to see if it will seal. It cleaned up pretty well.

Now of course I can't figure out how to get it back in. The outer seal rolls back, and I can't seem to get it to curl around the piston. Just going to get jammed up. Is there a trick to getting the piston back in? Seems like I need to take the outer seal out and place it on the piston first.

Thanks for the advice. Worse case now I have to buy a rebuild kit so it has been a good weekend.
Regards,
Peter in Austin

[George Ryals]

DOH! Native you are right. So just heating the caliper up should do the trick.

[Major Softie]

Seen 9mm and 40 caliber. Have yet to see 40mm caliber.

[R80/7_Peter]

Funny, I must have been thinking I may need a gun to get it out? But is there a trick to getting it back in?
Thanks,
Peter in Austin

[Major Softie]

Awwww, man: you fixed it!

It was much more fun the way it was.