How mechanically inclined are you? (OP). Do you have access to an air compressor? First check the pads for looseness (they should be able to be moved when mounted). And then the caliper sliding pins for smooth movement. If that passes, could be gunk behind your piston. Or a crapped-out piston...or rusty bore.
The caliper might have a stuck piston. Doesn't go out well, doesn't go in well either. Remove the dust boot with a pick and check it out. If it's rusty on the piston sides where you can see chrome and rust, that means a cheapo replacement was probably put in there and it rusted up. Time for a new caliper. But if it's just brown on the sides then you might want to consider popping the piston out and have a look and clean things up. Assuming you have an air compressor. Chrysler usually uses phenolic pistons with is a brown plastic with a SS cap.
What I usually do in a stuck piston situation is remove the caliper & pop the piston out and have a look. Clean things up. Lube. Put back together an yer good for several more years. (assuming it's all clean in there). But if it's a rusty ole OReilly rebuilt caliper and there's rust on the piston (the actual caliper piston) then you might as well go get a new one. They use cheap pistons which rust up quick in the rust belt. Couple yrs. And the dust boots they use are thin and cheap and crack (letting in moisture). I like OReilly Auto...and I think most rebuild calipers are like this from other places too. Oh ...and they sandblast the caliper bores (which effectively ruins the caliper). If you need a new one, and you don't want to dig in further, go buy a brand new Premium caliper from Carquest or Advance Auto. Costs a lot more but it's a superior product like OEM. You'll buy 3 OReilly rebuilt calipers in the span of one Advance Premium caliper...so in the end you saved a lot of work.
If you have the skills and want to dig in ....To remove the caliper piston and have a look or rejuvinate, remove the caliper first. Prepare by having a strip of rubber (inner tube rubber will work) and put a C-clamp or vise grip and a couple washers....and clamp the rubber around the brake hose as soon as you remove it from the caliper ....so it doesn't leak fluid all over the place. Then you can work on the caliper w/o creating more brake work for yourself (more bleeding than necessary). Add some fluid to your reservoir if need be so you Never run it dry.
Remove the rubber caliper piston boot first. Take a very small screwdriver of pick and "Gently" get under the rubber part on the caliper and gently remove and peel the boot edge off it's seat and from the caliper piston. Or remove the whole thing from the caliper if you can. Don't damage it, you need to reuse it. Some have a metal flange on the rubber you need to gently pry up. Once the dust boot is off, Put a large C-clamp on the caliper and piston somewhat loose and some compressed air on the caliper inlet. You might need to put a piece of vacuum hose over your blower tip to make a seal.
Apply the air gently. The piston will move out until it is stopped by the C-clamp. Then loosen the clamp another 1/2" and let it come out some more...repeat. At some point when the piston is out far enough you should be able to remove it with your fingers (not while using compressed air!). Keep your fingers away so they don't get pinched or mangled. You don't want too just pop the piston out b/c they can fly across the room and bust. And NEVER use a pliers b/c chrysler uses phenolic pistons which are like a bakelite plastic and they WILL break. (Rock Auto probably sells replacements).
A caliper can look terribly rusty on the outside but brand new inside if the fluid has been maintained/exchanged. I've seen 20 year old calipers that looked like the day they were made ...on the inside ...again, if the fluid was changed once or twice in the car's life. Once the piston is out, inspect the parts and determine what you have. If all good, clean out any debris and goo... and clean the remove rubber o-ring (remember it's orientation in case there is a micro-curve cut on one side). If it all looks good inside, grease with some brake grease and reassemble. If it doesn't ...time to go buy a different caliper.
If you did all that, reinstall caliper and bleed out per normal. Again, if this seems like something you aren't comfortable, haven't done, or don't have experience with, don't do it. Have the brakes done by a competent brake shop.
