Magnetic fluid seals are well known for their zero-leakage performance but are limited at high rotational speeds due to heat generation and fluid loss. This study experimentally investigates the failure mechanisms of ester-based magnetic fluid seals at high speeds, specifically focusing on thermal dissipation and fluid loss. A custom-designed high-speed rotary seal test platform was developed, and experimental studies were conducted to evaluate sealing performance. Our results showed significant temperature increases and fluid loss at higher rotational speeds, with a noticeable fluid ejection phenomenon occurring at approximately 13.7 m/s, and the sealing gap temperature reached 92 °C at 9000 rpm under uncooled conditions. This study experimentally verified that the main failure mechanisms of magnetic fluid seals at high speeds are centrifugal force and thermal dissipation, and proposed future design directions. This research provides key insights into the failure of high-speed magnetic fluid seals and offers a potential approach for improved high-speed sealing performance.