Driver side brake pistons not retracting

[J-440]

Have the 13" Wilwood/6 piston caliper kit. Everything is new. My driver's wheel is not spinning when the brakes are released. The other 3 are fine. I remove the pads (I have to pry them out), then step on the brake pedal and it's pretty soft. I check what the 6 piston are doing and 3 are retracted and the other 3 are not. I take the caliper off, inspect all pistons and o-rings for wear and rust, put em back in and reinstall the caliper. Put the pads back in, vacuum bleed the driver's side, step on the pedal, and I'm back to where I started. Any ideas?

[69L48Z27]

I have some thing similar going on except it's not just one side. When it's locked up crack a brake line or bleeder and see what it does.

I have mine narrowed down to the master cylinder not releasing pressure. It's almost like I have to shim the master cylinder away from the booster. Mine is a 9" dual diaphragm booster which is new. And a C6 new master cylinder. Wilwoods front and rear, all new.

[69L48Z27]

I fixed my issue. The master cylinder is a recessed type and the booster was setup for flush MC. Took 1/4" off the booster rod and everything works perfect.

[J-440]

Took it apart, polished the pistons and put it back together. I'm gonna see what happens this weekend.

[J-440]

Nope it's still doing the same thing. I even bled the entire system starting with the passenger rear wheel. When I took the caliper apart, the pistons and O-rings were fine. I used a 1 person vacuum pressure bleeding system also. Any ideas before I call the wife and do it the old-fashioned way?

[DreamRyder1963]

What brake hoses are you using? Stainless steel or old school rubber? I had a vehicle with a similar issue and it was a partially collapsed hose.

[J-440]

Got all stainless hoses. Yeah I heard that rubber hose can act as a choke point for the fluid.

[J-440]

Apparently my old vacuum bleeder has seen better days. I had my wife pump the pedal and quite a bit of air came out of the driver side caliper. Re-bled the passenger side as well and now my calipers are functioning normally. Thanks for the help brothers.