2010 grand caravan sxt rear brake problem
 

I just had my rear brakes and drums replaced. I feel the brake pedal dropping when i press it. I asked my mechanic about he.. he told me to drive it around for a day cause the piston need to screw out since he had to screw it in to replace brakes.
???? WTF??? i never heard this before..

Please help.

I would question the guy too. If you have rear drums on your vehicle, then the piston don't screw out. On rear disc brakes the piston only screws out for the park brake adjustment. Are you sure that vehicle has rear brake drums? The reason I ask, is most of the minivans have rear disc brakes.