OEM 2004 GMC Sierra 1500 Brake Master Cylinder

2004 GMC Sierra 1500 Parts Questions & Experts Answers

• Q: How to overhaul the brake master cylinder on 2004 GMC Sierra 1500?

  A: To overhaul the Brake Master Cylinder, first out it from the vehicle, then secure the mounting flange in a bench vise making sure the rear where the primary Piston is. Clean the area surrounding the reservoir cap before removing it as well as the diaphragm and checking them for cuts, cracks, nicks or deformation and replace if any parts are found to be affected. Remove the master cylinder reservoir, using a smooth, round-ended tool, depress the primary Piston and take out the Piston retainer, then remove the primary Piston assembly from the cylinder bore. Bridge the cylinder inlet ports and rear outlet port then have a low pressure, non-lubricated, filtered air fed into the front outlet to remove the secondary Piston with the primary and secondary seals as well as the spring and dispose of it. Clean the master cylnder, secondary Piston, and return spring interior and exterior with denatured, then inspect for cracks, scoring, pitting or corrosion and replace the master cylinder if any is found. Dry all components with non-lubricated, non-oiled air that is filtered and lubricate the master cylinder bore, secondary Piston, return spring, and all overhaul components with delco supreme 11® l brake fluid (GM P/N 12377967) or equivalent dot-3 brake fluid from a clean, sealed container. Mount the lubricated new primary seal and retainer along with the new secondary seal onto the secondary Piston and mount the lubricated return spring and secondary Piston installation into the cylinder bore then support the lubricated new primary Piston installation. Depress the primary Piston of a round ended smooth tool to install the new Piston retainer, re-attach back the master cylinder reservoir and its cap and diaphragm and then attach it back onto the vehicle.