Compensator Port Test

PROPER OPERATION
The purpose of the compensator ports in the brake master cylinder is to:
- Supply additional brake fluid from the brake master cylinder reservoir required by the brake system due to brake shoe and lining wear.
- Allow brake fluid to return to the brake master cylinder reservoir when the brakes are released.
The returning brake fluid will create a slight turbulence in the brake master cylinder reservoir. This is a normal condition and indicates that the compensator ports are not clogged.
Clogged compensator ports may cause the brakes to "hang-up" or not fully release. If clogged compensator ports are suspected, proceed as follows:

TESTING
1. Raise and support the vehicle. Wheels should be able to be rotated.
2. With the brakes released, attempt to rotate each wheel. If an excessive amount of brake drag exists, continue with the test. If an excessive amount of brake drag exists at only one wheel, it indicates a possible seized disc brake caliper, rear wheel cylinder, or parking brake component. Repair or replace components as necessary.
3. Check the brake on/off (BOO) switch, brake pedal freeplay, and brake master cylinder to power brake booster push rod adjustments to verify that the brake pedal is not partially applied.
4. Loosen the nuts attaching the brake master cylinder to the power brake booster and pull the brake master cylinder away from the power brake booster.
5. Repeat Steps 1 and 2. If the brake drag disappears, the power brake booster is binding and must be replaced. If the brake drag continues, the brake master cylinder is binding and must be replaced.