Brake Master Cylinder - Compensator Port
WARNING: This page is about a different car, the 2007 Mercury Mariner and 2007 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.
The purpose of the compensator ports in the brake master cylinder is to:
- supply additional brake fluid from the brake master cylinder reservoir needed by the brake system due to brake lining wear.
- allow brake fluid to return to the brake master cylinder reservoir when the brakes are released. The returning brake fluid creates 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:
- With the vehicle in NEUTRAL, position it on a hoist. Refer to JACKING AND LIFTING article.
- 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 brake disc caliper, brake wheel cylinder, or parking brake component. Repair or install new components as necessary.
- Check the brake stoplamp switch adjustment and the brake pedal free play to verify that the brake pedal is not partially applied.
- 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.
- Repeat Steps 1 and 2. If the brake drag disappears, the power brake booster is binding and a new one must be installed. Refer to POWER BRAKE ACTUATION article. If the brake drag continues, the brake master cylinder is binding and a new one must be installed. Refer to HYDRAULIC BRAKE ACTUATION article.