Brake caliper pistons not retracting

[J-440]

Am using braided steel line with no tape whatsoever. The outside pad slides out no problem, but the inside pad I have to pry out. The pistons are only about 1/8" sticking out on the defective side, the other side the pistons are flush with the caliper.
What causes the pistons to retract anyway? When you release the pedal, is a suction created to draw the pistons away from the pads?

[GregWeld]

Originally Posted by J-440

Am using braided steel line with no tape whatsoever. The outside pad slides out no problem, but the inside pad I have to pry out. The pistons are only about 1/8" sticking out on the defective side, the other side the pistons are flush with the caliper.
What causes the pistons to retract anyway? When you release the pedal, is a suction created to draw the pistons away from the pads?

Good question about the suction -- there might be a teeny amount - but it would be minuscule. The pad is generally just resting on the rotor and the flex of the rotor will push the pad back (we're talking really small movements here). New cars with fancy ABS brakes will sometimes have a feature where if you turn on your wipers they figure your brakes (rotors) are wet and they'll apply a small amount of pressure just to dry them off.

Sounds to me like you have a bad caliper.

Since it's only the one caliper that's acting up... otherwise I'd be asking you about your complete system - like your residual valve etc. And some Masters have residual valves built in.. but your other caliper is acting normal so we're just worried about the one.

[68Cuda]

Originally Posted by J-440

Am using braided steel line with no tape whatsoever. The outside pad slides out no problem, but the inside pad I have to pry out. The pistons are only about 1/8" sticking out on the defective side, the other side the pistons are flush with the caliper.
What causes the pistons to retract anyway? When you release the pedal, is a suction created to draw the pistons away from the pads?

The flex of the square O-Ring seal and the knock back from any rotor run out is what draws the pistons back. If it is easy enough to swap the caliper left to right then try that to determine if it is caliper or the system. (Are your bleeders and bypass easy to swap) Does your mount have shims to center the caliper? Sounds like you might be off center also. All this stuff is harder to troubleshoot when you have to rely on someone else to look and touch...

[Vegas69]

Good call Michael, the caliper should be centered on the rotor. It's not uncommon to need to pry on a brake pad to remove it. I'd check the center of the caliper and drive it.

[J-440]

That's what I thought the problem was at first, that the caliper wasn't properly shimmed to fit over the rotor. But it's fine. Unfortunately I can't swap calipers, it's a one size fit only system. I'll keep yall informed in case this happens to anyone else. Thanks for all the input!!

[J-440]

Time to invest in another vacuum bleeder kit bc my old one just won't cut it anymore. Had my wife pump the brakes and quite a bit of air came out. Did the passenger side and now everything's back to normal. Life is good!