Abstract: A system such as one for detecting when a hydraulic fluid system adapted to a turf care machine, has developed a leak and to warn the machine operator of such a leak before an appreciable amount of hydraulic fluid is allowed to leak from the system. The system includes a reservoir for holding a quantity of hydraulic fluid. The reservoir is connected via a connecting tube or hose to an expansion tank mounted adjacent to the reservoir. The expansion tank includes a fitting having an elongated tube extending down into the expansion tank. The end of this tube is maintained substantially below the level of hydraulic fluid in the expansion tank during operation of the turf care machine to which it is attached. As the machine is operated, the hydraulic fluid expands with rising temperature, and the connecting tube communicates the expanding fluid to the expansion tank. When operation of the machine is discontinued the hydraulic fluid contracts as it cools.