A heat exchanger monitoring system includes a heat exchanger 11 capable of receiving a flow F of a working fluid therethrough. A first sensor 12 is disposed upstream of the heat exchanger 11 for measuring at least one property of fluid relating to an amount of contaminant material carried by a first flow entering the heat exchanger 11 and configured to output a first sensor signal indicative of the measured property of the fluid. A second sensor 14 is disposed downstream of the heat exchanger 11 for measuring the same property of the fluid relating to an amount of contaminant material carried by a second flow exiting the heat exchanger 11 and configured to output a second sensor signal indicative of the measured property of the fluid.