Non-Pressure Leaks

Two parts of the brake system that may have a brake fluid loss that does not appear when the system is under pressure are the brake master cylinder reservoir and the brake caliper under the following conditions:

Reservoir

• Missing or poorly-fitted brake master cylinder filler cap
• Missing or damaged brake master cylinder filler cap gasket
• Punctured or otherwise damaged brake master cylinder reservoir
• Missing, damaged or poorly-fitted sealing grommets between the brake master cylinder and the brake master cylinder reservoir

The brake master cylinder reservoir grommets are not serviceable and must be installed new as part of a new reservoir assembly. Refer to Brake Fluid Reservoir in HYDRAULIC BRAKE ACTUATION article.

Caliper

• Foreign material in the caliper piston seal groove
• Punctured or otherwise damaged caliper piston seal

The brake caliper piston seals are not serviceable and must be installed new as part of a new brake caliper. Refer to FRONT DISC BRAKE article for front disc brakes or REAR DISC BRAKE article for rear disc brakes.