Seized rear caliper

[Stanipkiss]

Need some help to find the cause of seized rear brake caliper!
Cleaned the car and took it for a drive to dry it off and when I got back and reversed it on to my drive, got out and the brake was smoking like hell and stank!
My solution today was from the Clarkson school of mechanics, I took the wheel off and whacked it with a hammer and it solved the seize. But I cannot keep doing this if it keeps seizing!

What could have been the cause?
The car is kept in the garage overnight without the handbrake on!

Thanks in advance.

[Chris92]

Maybes the rubber boot/seal on the piston has a rip in it letting crap in.

[Human Joist]

It will be either the sliders on which the caliper moves are dirty rusted and sticking or the piston itself. The rubbers split let water in and seize. Strip it back and clean and grease. If when you do so you see the rubbers are split on either the sliders or piston you can order a repair set which includes all the bits as well as new piston.  There are plenty of guides on here bud

[doylebros]

I'm assuming the other side is working correctly - releasing when the handbrake is released?

If so it's pretty much as the last poster stated.