Brake Caliper Piston won't decompress

On a kart I help my friend work on, the brake caliper piston always stays engaged and never goes back in. What are some ways that this can be fixed?

Take of caliper, take some knipex pliers and pres them in? It can also be that a seal has folded inside

Chris can you explain this further…when you say engaged do you mean the pad stays close to the rotor or is it actually grabbing the rotor and the axle won’t spin?

In either case, I would first ask if the system (caliper and master cylinder) has been rebuilt with new o-rings and seals?

when I press the piston back in after pumping/pressing the breaks it goes back to the piston being out.

The axel is not locked sometimes it does lock up. There is basically no movement in the pedal, it instantly locks up when you press the brake pedal. No, it has not been rebuilt.

Have you tried removing all fluid and putting fresh fluid and bleed it? Try ordering a rebuild kit for them and take appart clean and new seals

Not yet I didn’t know if something like this happened if it needs a full rebuild or if a full brake flush could fix it.

What brand of brakes are they and how old? When I first got into this I had a CRG that had been sitting for about 8 years. In that time the aluminum had corroded inside the caliper and the brakes didn’t work right. In your case based on what you are saying, the issue could be the master cylinder or the caliper or possibly both. A complete rebuild might take care of it.

The other thing. Depending on the design the pistons may not fully retract but enough to allow for the axle to spin freely.

Some calipers have springs that help retract the pads/push the piston back in. Besides everything else mentioned, make sure you aren’t missing some springs or other components.

What brand brake system is it? Designs vary and it will help in diagnosing your issue. The cheapest first step would to be to flush and bleed the entire system. An air pocket at the piston will push it back out and get worse as the pads heat up, leading to a lock up.

I had a problem on my rain kart… piston got stuck and didnt move a millimeter. Somehow i managed to Seize a brake caliper🤣

OTK brakes don’t fully retract on pedal release. Only just to the point of not being engaged. But they do disengage and the axle spins freely.