OEM GMC C3500 Brake Master Cylinder

GMC C3500 Brake Master Cylinder Parts and Q&A

• Master Cylinder
  19209223
  Q: Is it essential to replace the brake master cylinder body instead of honing the bore during an overhaul on GMC C3500?

  A:

  The procedure of overhauling a Brake Master Cylinder requires cylinder body replacement instead of bore honing since honing damages the hard and polished surface which results in accelerated rubber cup wear. Start by removing the reservoir cap before draining out the brake fluid from the reservoir. Proceed by removing the reservoir along with the two grommets from the master cylinder body before securing the master cylinder mounting flange in a vise. Start by removing the snap ring and primary Piston assembly and then proceed to remove the seal. When using air pressure to extract the secondary Piston position the open bore end 25 mm (1 inch) above a padded surface while carefully applying pressure to catch the Piston ensuring you do not point the bore at any person. Follow these steps after you remove the secondary Piston: seal and spring retainer removal from the master cylinder body using air pressure through the front port then removing the spring and secondary Piston from the master cylinder body. All parts will need cleaning with approved solvents following theprotocol of denatured alcohol for metal components and clean brake fluid for rubber parts. Perform an assessment on the diaphragm condition and inspect the cylinder bore for scoring and corrosion with master cylinder replacement required for damage discovery. Examine the reservoir for any signs of cracking. When putting everything together apply clean dot 3 motor vehicle brake fluid as a lubricant to all grommets and seals and the cylinder bore while employing fresh seals. Begin by installing the secondary Piston spring and spring retainer after which put the primary seal and secondary seal onto the secondary Piston. First insert the secondary Piston into the master cylinder body and place the primary Piston seal and primary Piston assembly afterward. Secure the assembly by using the snap ring which compresses the primary Piston at the right level before installing new grommets together with the master cylinder reservoir and its cap.
• Overhaul Kit
  18022005
  Q: How to properly bench bleed a Brake Master Cylinder before installation on GMC C3500?

  A:

  Bleeding the Brake Master Cylinder first on the bench helps you work faster during the brake system hydraulic bleeding process. Place the outlet ports in first then attach the master cylinder to a vise at a slight angle with the front side pointing downward. Insert clean brake fluid into the container and push the primary Piston 25 mm several times using even strokes of a round-ended tool. The Piston does not reach its full stroke when air escapes from the system. Afterward position the master cylinder vertically with an upward tilt and stroke the Piston just like before. Place the master cylinder in the vise with its front lower down and remove the plugs from the outlet ports for one-by-one operation. Push the Piston toward the bore to remove air from the cylinder before fastening the plugs and letting the Piston return to its normal position to keep new air out. Place pure brake fluid in the reservoir and execute standard brake fluid bleeding steps when the master cylinder is installed.