2005 Elantra replaced front caliper pistons
 

My car has 70000 miles on it and was developing what I thought was just warped rotors.

I took in to the dealer and the service guy said he couldn't find anything wrong with it.

I took it to Just Brakes because there was something wrong and the guys there found my rotors warped and the piston on the calipers sticking. They showed me the bluing on the rotors due to overheating.

Have any of you had to rebuild your caliper pistons due to this issue?

Actually, that is somewhat common on Hyundais driven in areas where salt is used on the roads during the winter.

2005 Elantra replaced front caliper pistons
 

Never had one apart. Automotive calipers have a dust/water boot that seals into the caliper and the end of the piston. FJR does not have this?