Q: Where is the Master Cylinder Located and How is it Replaced?
A: The brake master cylinder is located in the engine compartment mounted to the power Brake Booster. On Durango models with ESP, remove the inner fender splash shield. Remove the fasteners for the fuse and relay box tray to move it slightly forward for clearance when removing the brake master cylinder. Remove as much fluid as you can from the reservoir with a syringe. Place rags under the fluid fittings and prepare caps or plastic bags to cover the ends of the lines once they are disconnected. Loosen the fittings at the ends of the Brake Lines where they enter the brake master cylinder. Disconnect the electrical connector at the brake fluid level switch on the brake master cylinder reservoir, then remove the nuts attaching the brake master cylinder to the power booster. Keep the brake master cylinder level while carefully pulling it off the studs and out of the engine compartment. If a new brake master cylinder is being installed, remove the fastener securing the reservoir to the brake master cylinder then pull up on the reservoir to remove it from the brake master cylinder. Transfer the reservoir to the new brake master cylinder. Bench bleed the new brake master cylinder before installing it. Attach a pair of brake master cylinder bleeder tubes to the outlet ports of the brake master cylinder. Fill the reservoir with brake fluid of the recommended type. Slowly push the pistons into the brake master cylinder - air will be expelled from the pressure chambers and into the reservoir. Repeat the procedure until no more air bubbles are present. Remove the bleed tubes, one at a time, and install plugs in the open ports to prevent fluid leakage and air from entering. Install the reservoir cap. Install the brake master cylinder over the studs on the power brake booster and tighten the attaching nuts only finger tight at this time. Thread the brake line fittings into the brake master cylinder. Fully tighten the mounting nuts, then the brake line fittings. Connect the brake fluid switch electrical connector. Fill the brake master cylinder reservoir with fluid, then bleed the brake master cylinder and the brake system. On Durango models with ESP, replace the fuse and relay box tray and the fender splash shield. Test the operation of the brake system carefully before placing the vehicle into normal service.