What does a geyser from the master cylinder reservoir indicate?

• A. Air is trapped in the system.
• B. Normal master cylinder operation.
• C. Brake fluid contamination.
• D. Low brake fluid levels.

Answer: (A)

A geyser from the master cylinder reservoir is a clear indication that air is trapped in the braking system. When air becomes trapped, it creates pressure inconsistencies that can manifest as spouts or geysers in the fluid. This is because the air compresses more than the brake fluid when pressure is applied; as the brake pedal is pushed, the air may be forced out of its current position with considerable force, causing the fluid to spray out of the reservoir. This phenomenon highlights the necessity of proper bleeding of the brake system to ensure that all air is removed and the hydraulic system operates as intended.

Normal operation of the master cylinder does not produce such geysers, and such behavior is not a result of brake fluid contamination or low fluid levels, although each of those conditions can also affect braking performance in different ways.