<![CDATA[Purpose: This study aimed to design and validate an Internet of Things (IoT)-based multi-parameter monitoring system for assessing DOT 3 brake fluid conditions through continuous measurement of moisture content, temperature, and fluid volume, supported by real-time visualisation and early warning functions. Design/methods/approach: A research and development approach was employed to integrate capacitive moisture, RTD PT100 temperature, and VL53L1X distance sensors with an ESP32 microcontroller, a Firebase Realtime Database, and a Flutter mobile application. Laboratory validation involved repeated measurements against reference instruments, followed by communication testing and limited single-vehicle-function verification. The sensor performance was evaluated using measurement error and agreement metrics. Findings: The developed system demonstrated close agreement with reference measurements and consistent sensor performance under controlled laboratory conditions. Cloud communication enabled continuous data synchronisation, whereas the mobile application successfully displayed monitoring information and generated alerts under simulated abnormal conditions. Single-vehicle verification further confirmed the functionality of the integrated sensing, communication, and warning mechanisms. Research implications/limitations: The system provides a practical foundation for condition-based brake fluid monitoring and preventive maintenance support. However, short-duration testing, single-vehicle verification, and simulated abnormal conditions limit the conclusions regarding long-term reliability and operational safety. Originality/value: This study demonstrates the integration of multi-parameter sensing, moisture-dependent temperature thresholds, cloud connectivity, and mobile early warnings within a unified DOT 3 brake fluid monitoring architecture.]]>
