A method for controlling operation of a heat exchanger system comprises providing a heat exchanger system mountable to a rear door of a rack mounted computer system, circulating a heat transport medium through the heat exchanger system, detecting leaks in the heat exchanger system by comparing a first flow rate in an inflow line to a second flow rate in a return flow line, emitting a leakage alert and ceasing further circulation of the heat transport medium through the heat exchanger system when the first flow rate exceeds the second flow rate by a predetermined flow amount, optimizing operation of the rack mounted computer system by monitoring an interior temperature of the rack mounted computer system in a plurality of vertical zones, and optimizing operation of the heat exchanger system by comparing a second temperature measured by a second temperature sensor in the return flow line with a predetermined maximum return flow temperature value.