I am putting this in the lounge because it's not HHR related.

Our 2009 Chrysler Town and Country hadn't been driven in a month or so. The pedal feels very soft, going down low. I looked at the rear brakes (which have discs and the parking brake is the type that screws the piston in and out). I saw why the pedal was sinking so low. The pads are worn down to about 1/3 of the pads left. However, the caliper piston retracts all the way in when you are not pressing the pedal, leaving a gap between the piston and the inner pad. The pedal has to be pushed down quite a bit before the piston extends enough to contact the back of the pad. What is causing the piston to be sucked back in (about 1/4") when you release the pedal? I replaced the caliper a few years ago and put in new pads and rotors.

Is this a caliper defect or something else? I haven't seen this particular problem before with disc brakes. After all, any disc brake caliper piston COULD retract fully every time, but the system doesn't generate a "vacuum" to suck it back in, it just removes pressure and the rotor runout moves the pads away a tiny amount.

Steve

 

On front calipers it is the square cut O-ring that pulls the piston back, not hydraulics. I have never dealt with rear calipers

 

Have you adjusted the parking brake ? That should remove the gap. Or replace the rear pads. (Best bet).

 

I took a look at Mitchell. I think there is a caliper lever return spring in play, it is part of the parking brake. Maybe the slider pins are sticking.

 

I do know this, the callipers need to be serviced and the pads of course need to be changed. A residual check valve could be the reason for the retraction allowing with the square cut o ring.