Envoy 2WD V6-4.3L VIN W (1998)
Brake Master Cylinder: Service and Repair
Master Cylinder Overhaul
DISASSEMBLY PROCEDURE
NOTICE: Do not hone the master cylinder bore. When the brake master cylinder is overhauled, it is recommended that the cylinder body be
replaced rather than CLEANED UP by honing the bore. The master cylinder has a hard, highly polished BEARINGIZED surface, which is
produced by diamond boring followed by ball or roller burnishing under heavy pressure. Honing will destroy this hard smooth surface and cause
rapid wear of the rubber cups.
1. Remove the cover.
2. Remove the diaphragm.
3. Drain the brake fluid from the reservoir.
4. Remove the reservoir and two grommets from the master cylinder body.
5. Clamp the master cylinder mounting flange in a vise.
6. Remove the snap ring.
7. Remove the primary piston assembly from the master cylinder body.
CAUTION: If air pressure is used to remove the secondary piston, place the open end of the cylinder bore approximately 25 mm (1 inch)
from a padded workbench or other surface to catch the piston when it comes out of the bore. Apply low air pressure very carefully to
