How to remove a seized caliper piston

I ran into this issue today whilst prepping the Junkyard sourced calipers for the new project. 2 of the pistons were seized tight. One came free after some acetylene based heat and a slide hammer but the other just wasn't going anywhere and the only lip I could use to apply force was crumbling.

OK first step. Order a new piston. This sucker is shot.

Step two clamp the caliper in the vise and drill right through the center of the piston with a #3 bit. Tap that new hole to 1/4-28

Obviously you have to be careful to not drill straight through the caliper. There is gonna be a gap there. Wait for it and you will feel it, then stop drilling. No brainer.

Now lube up the threads of a 1/4-28 bolt with some anti-seize or whatever is handy and drive that sucker in. When the bolt hits the bottom of the bore just keep going and it will push the piston out.

Using an electric impact driver it took about 30 seconds to push this bastard out. It was in there tight

Total time spent. Maybe 3 minutes. New piston cost $5. That beats the hour I spent damaging the thing with a vice grip slide hammer and torch getting nowhere. I bet if I hadn't buggered up the dust seal lip so much I could have welded the threaded hole back up and reused it.

Nice... Looks like a great idea..

Sweet! I'll try that if I get one that doesn't come out with hydraulic pressure. So far I've been lucky.

Nice tip, great approach

Years ago, when pistons were expensive and labor was cheap, we used this technique: install a Zirc fitting in the brake line port, and pump in grease from the grease gun. Thousands of psi beats hundreds every time.

In reply to injuneer:

That trick works well unless you have multi piston two piece calipers like these. There is no way to block off all the passages and piston ports.

C-clamp or block of wood will hold the non-siezed pistons in a multipiston caliper.

Random chunks of 2x4 are awesome to have around the workplace. You can make all sorts of quickie blockup tools/retainers/etc with some scrap lumber and your reciprocating saw of choice. Last week it was a chunk to hold the torque converter in a car that was leaving the shop sans engine. A V-notch of the right depth kept the block snug between the converter and the bar that was slung across the framerails to hold the trans up. Took less time to make than trying to fangle together the right combination of bent strapping/old wrench to hold the converter in like junkyards do.

Knurled wrote: C-clamp or block of wood will hold the non-siezed pistons in a multipiston caliper.

But then you would still have the two o-ring sealed fluid transfer ports to deal with. If it were a wilwood or dunlop style caliper with external lines then that is my go to method but with these Toyota or some Brembo and Tokico multipiece units sacrificing the sub $5 piston makes a lot of sense and is a lot less messy than cleaning up all the grease.

Knurled wrote: C-clamp or block of wood will hold the non-siezed pistons in a multipiston caliper. Random chunks of 2x4 are awesome to have around the workplace. You can make all sorts of quickie blockup tools/retainers/etc with some scrap lumber and your reciprocating saw of choice. Last week it was a chunk to hold the torque converter in a car that was leaving the shop sans engine. A V-notch of the right depth kept the block snug between the converter and the bar that was slung across the framerails to hold the trans up. Took less time to make than trying to fangle together the right combination of bent strapping/old wrench to hold the converter in like junkyards do.

I do as well. I also keep a pack of those wood shims they sell at the home improvement stores for squaring up door jams and windows frames when you install new ones. Two of them used together will fill a gap and by sliding them together they wedge themselves in and lock things in place.