Brake help

[geospider]

Trying to rebuild front calipers. having trouble getting piston out of the caliper. have heard about blowing out with compressed air: hard to get a seal. The pistons seem stuck solid; can't even easily push the pistons back in.
Ideas.
brakes worked OK prior to front end redo.
Thanks all.
Geo

[Frog2Spider]

Soak them in a product called Blast, or diesel fuel. Yes, compressed air is the method commonly used.
A better idea, if the budget allows, buy new calipers.

Dave.

[lglade]

Mine were stuck too, and I used a BAS (big ass screwdriver) to carefully push the piston back into the caliper. And that movement loosened the piston enough that compressed air could pop it back out. But, be super-careful when using compressed air to remove the piston, and use a chunk of wood inside the opening of the caliper to 'catch' the piston as it comes out.

The piston will come out with a *bang* when the pressure finally overcomes friction, and there is enough energy TO SMASH OR REMOVE A FINGER . So insert the wood and wrap a shop towel around the caliper, then make sure your fingers are clear before hitting it with the air. Mine took 90+ psi to get the pistons out, but once they were out the rebuild process was a piece of cake.

[geospider]

thanks, will give a try today. sprayed some blaster around the outside edge. hard part with the air is getting it sealed enough, esp if it takes that much pressure. I have read about the piston flying out. thanks for the safety reminder.
update as I go.

on the VERY positive side: head returned from machine shop: looks brand new with cam boxes on and lash all done. gotta love these shops that care about their work.

[lglade]

I have an air blow gun with a conical rubber tip and it seals up tightly against the caliper. You can pick one up at Harbor Freight for less than $10.

[geospider]

Got them out. Yest quite the bang.
My Harbor freight did not have the rubber cone, so building up some duct tape (the universal tool) worked and they are now rebuilt.
Thanks you guys.

Geo

[lglade]

Cool and congratulations!

[MikeHynes]

The easiest way to remove the pistons is to use the hydraulic pressure the brake system produces. You can simply remove the caliper and pads (without removing the brake lines) then carefully pump the brake pedal. Most often one piston will move first/farthest, use a c clamp to keep it from coming completely out until the other piston(s) are far enough out to come out easily with a little air pressure. Those buggers can be very tight, but not tight enough that the hydraulic pressure won't push them out.