Mercury 6W1Z-2140-AA Master Cylinder Assembly

For the overhaul, mount the master cylinder in a vise, remove the pressure control valve, and extract the primary piston snap-ring and the primary and secondary piston assemblies. Clean the master cylinder body and components with brake system cleaner, avoiding petroleum-based solvents. Inspect the cylinder bore for corrosion and damage, replacing the body if needed. Lubricate new reservoir grommets with silicone grease and press them into the master cylinder body. Lay the reservoir on a hard surface and press the master cylinder body onto it. Lubricate the cylinder bore and piston assemblies with clean brake fluid, then insert the secondary piston assembly followed by the primary piston assembly. Install the snap-ring and, if equipped, the stop bolt with a new sealing washer. Inspect the reservoir cap and diaphragm, replacing damaged parts.

Before overhauling the master cylinder, it is essential to consider factors such as the availability and cost of a new or factory-rebuilt unit, as well as the availability of a rebuild kit.