04 express 3500 brakes apply by therself after 1 block notice also dont have to push brake pedal to get out of park anytime brakes release after sitting awhile pulled master cyl off plunger back all the way pedal works fine this way when brakes are set up pedal is very hard and barely moves any help would b appreciated
Could maybe be this check valve, click on image. The check valve is supposed to prevent exactly what you describe..once the brakes are applied the fluid must 'retreat' back to low pressure side. In you van it seems it isn't.
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