Non-Pressure Leaks

WARNING: This page is about a different car, the 2008 Mercury Mariner and 2008 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.

Two parts of the brake system that could 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 brake fluid reservoir. Refer to HYDRAULIC BRAKE ACTUATION article.

Brake 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.

Wheel cylinder

Foreign material in the wheel cylinder seal
Punctured or otherwise damaged wheel cylinder seal

For additional information on servicing the wheel cylinder, refer to Disassembly and Assembly in DRUM BRAKE article.