The best thing you can do is replace the caliper.
If the brakes are disc brakes then try opening the bleed screws on the calipers and see if the pressure releases if not then remove the calipers and replace because the piston is probably frozen or you can try pushing in the piston with a c-clamp,if that doesnt work replace the calipers as noted. If the brakes are drum brakes then check your brake cylinders to see if they are leaking if so you can usually rebuild them if not then replace them and bleed your brake system to get brakes back to normal, you can also make sure your drum brakes are adjusted correctly.
If pads are bad you have to replace it, but it sounds like you have problems with calipers. Either you have to clean calipers or replace it. Check break fluid level. Check the breaking system, you might have some air in there.
If the caliper is sticking or you can't get the piston pushed back in it's best to just buy a new caliper.
Either your emergency brake is hanging up or your wheel cylinder is leaking fluid and needs replaced if drum brakes and if disc brakes the caliper could be bad.
Have them turned. If the caliper is not sticking they shouldn't warp again
This may be caused by rust on the piston or the cylinder. When you put the brakes on the piston can freeze up then. I had it happen on a Toyota & that's all it was . Do not attempt to fix it unless you know what you are doing. From the BigTomato.
Spongy brakes are usually a sign that the brakes need to be bled. This is an easy procedure that you can do yourself relatively cheaply or you can take it to a mechanic and it can be done for about $50. If the brakes need to be replaced you are looking at $75-$100 dollars per pair.
Change brand or composition of disc brake pads and resurface or replace brake rotors. Apart from the obvious worn pads, they will sometimes squeal if the anti-rattle shim is missing, between the back of the pad and the caliper piston. You could try anti-seize compound here (Copaslip). Check that the edge of the rotor has not got a build up of rust.
Rear disc ? if it is rear disc brakes there is a drum brake in side of the rear rotor that is your parking brake and has an adjuster in it if you pull the rotor off.
Estimate Front one side $380.00 Estimate Rear one side disc brakes $285.00
This problem is caused by disc brakes that have a fluid leaking from the calipers. You can buy loaded calipers an install to the car to fix the problem.
how do you fix brakes on a 2002 Cl 500 Benz