Standard drum master cylinder has a check valve built in. Not used with disc brakes. Could also be sticky pistons in caliper. Jack a wheel up and open the bleeder for a second and if it releases, it is not the caliper. If it releases, could be wrong master cylinder, faulty brake hose or master cylinder not retracting fully.Hi guys. Just wondering what master cylinder set up people are using on AP6 with 4 wheel discs. I have standard master cylinder with remote booster. 9” diff disc and cm calipers on front. Front brakes are sticking on and master cylinder is leaking out of lid. I’m thinking there is residual pressure building up in system. I am looking at a dual diaphragm offset booster and master cylinder from Hemi performance. Any advice would be greatly appreciated. Thanks.