Abstract: Disclosed is a method for monitoring the status of a motor vehicle engine cooling system including sensing the pressure and temperature of coolant in the cooling system, generating respective output signals, and processing the output signals to generate an indication of a coolant system fault condition when the pressure of the coolant falls below a preset limit in relation to the temperature of the coolant. Apparatus for performing the method is also disclosed. Several embodiments are disclosed for indicating a coolant system fault condition, such as adjacent gauges for visual comparison, summing of the signals to provide a combined output signal of temperature modified by pressure for display on a gauge, and/or comparing the signals to trigger a warning signal when the preset limit is exceeded.