Brake Master Cylinder - Non-Pressure External Leaks
A low brake fluid level in the brake master cylinder reservoir may be caused by the following non-pressure external leaks:
Type 1 . An external leak may exist at the brake master cylinder filler cap due to improper position of the cap, cap gasket, or cap gasket deterioration.
Type 2 . An external leak may exist at the brake master cylinder mounting flange due to internal seal failure. Repair or replace the brake master cylinder.
Type 3 . An external leak may exist at the base of the brake master cylinder reservoir due to deteriorated reservoir mounting seals. Repair or replace the brake master cylinder.