I think some newer calipers have threads such that the only way the piston will go back in is to screw it back in with the tool. I think you can tell if it is screw-in if it has indentions on the piston for a tool. My guess is the threads are an attempt to keep the pad snug as it wears to reduce the chance of chatter.
That's only in rear calipers and not all of them. It's because of the parking brake mechanism.
Funny I just did the brakes on the wagon... Replaced calipers/pads/rotors and hoses all for ~$80. The rubber slider pieces were so swollen that the caliper kept binding and dragging. The pads and rotor fit with a little room to spare for a change instead of being tight like on Rays burb. I did find that the intake gasket is starting to drip instead of just wet so that'll be a project for another day. Not too hard on the 3.3, not like a 3.1... Toss a 3.8 engine and trans in and a new pair of seats and it's ready for another 140K. The 3.8 would get allot better mileage and lots more power too. Basically a drop in as they use the same mounts on the subframe.
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