F 150 4WD Pickup V8-4.6L SOHC VIN W (1998)
Brake Master Cylinder: Component Tests and General Diagnostics
Bypass Conditions Test
1. Disconnect the brake lines at the brake master cylinder.
2. Plug the outlet ports of the brake master cylinder.
3. Apply the brakes. If brake pedal height cannot be maintained, the brake master cylinder has an internal leak and must be rebuilt or replaced.
Compensator Port Test
The purpose of the compensator ports in the brake master cylinder is to supply any additional brake fluid required by the system due to brake pad wear
and to allow brake fluid returning from the brake lines to the brake master cylinder to enter the brake master cylinder reservoir.
The returning brake fluid will cause a slight turbulence in the brake master cylinder reservoir. Turbulence seen in the brake master cylinder reservoir
upon release of the brake pedal is normal and shows that the compensating ports are not plugged.
