Chevrolet 91174779 Cylinder Asm,Brake Master (On Esn)

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Before deciding to overhaul the Brake Master Cylinder, check on the availability and cost of a new or factory rebuilt unit and also the availability of a rebuild kit. The Brake Master Cylinder is located in the engine compartment, mounted to the power brake booster. Remove as much fluid as possible from the reservoir with a syringe, placing rags under the fluid fittings and preparing caps or plastic bags to cover the ends of the lines once disconnected, taking care to avoid spilling brake fluid, which can damage paint. Loosen the tube nuts at the ends of the brake lines where they enter the Brake Master Cylinder using a flare nut wrench to prevent rounding off the nuts. Pull the brake lines slightly away from the Brake Master Cylinder and plug the ends to prevent contamination. Disconnect the electrical connector at the Brake Master Cylinder, then remove the two nuts attaching the Brake Master Cylinder to the power booster, and carefully pull the Brake Master Cylinder off the studs and out of the engine compartment. Before attempting the overhaul, obtain the proper rebuild kit containing necessary replacement parts and any specific instructions. Inspect the reservoir grommets for leakage indications and remove the reservoir as needed. Place the cylinder in a vise and use a punch or screwdriver to depress the pistons until they bottom against the other end of the Brake Master Cylinder, then remove the stop screw. Carefully remove the snap-ring at the end of the Brake Master Cylinder and take out the internal components, noting the order of the components, especially the two springs of different tension. Inspect the bore of the Brake Master Cylinder for deep scoring or damage, which would require a new unit. Replace all parts included in the rebuild kit, cleaning reused parts with clean brake fluid or denatured alcohol, and lubricate all parts liberally with clean brake fluid during assembly. Push the assembled components into the bore, install the stop screw with a new gasket, and install the new snap-ring properly. Before installation, bench bleed the Brake Master Cylinder by mounting it in a vise, inserting threaded plugs into the brake line outlet holes, and filling the reservoir with the recommended brake fluid. Remove one plug and push the piston assembly into the bore to expel air, replacing the plug before releasing pressure. Repeat until only brake fluid is expelled, then proceed to the other outlet hole. For an alternative method, cover the hole with a finger instead of replacing the plug during the bleeding process. Install the Brake Master Cylinder over the studs on the power brake booster and tighten the attaching nuts finger tight. Thread the brake line fittings into the Brake Master Cylinder, ensuring they thread in easily without stripping the threads. Tighten the mounting nuts to the specified torque and secure the fittings. Fill the Brake Master Cylinder reservoir with fluid, then bleed the Brake Master Cylinder and the brake system, testing the operation of the brake system carefully before placing the vehicle into normal service.