I have a problem with the ABS system on the rear brakes of my F250 (has disc brakes on the front). It has a new master cylinder, new ABS valve unit (bolted on frame uder driver's seat), and the rear brakes and brake cylinders are new. I have a hard pedal when the engine is turned off. When I start the engine the brake pedal goes mushy.
Appreciate any help I can get on my problem