In an exemplary embodiment, a method to control excessive temperature changes in a coolant circuit includes providing a coolant circuit including a bypass flow pathway bypassing a heat exchanger, said coolant circuit at an elevated operating temperature; providing an adjustable coolant flow through said bypass flow pathway and said heat exchanger; providing a coolant pump in said coolant circuit; determining a temperature change in said coolant circuit in response to initiating a coolant flow from said heat exchanger into said coolant circuit, said temperature change greater than a predetermined limit; and in response to said determined temperature change, adjusting at least one or more of said coolant pump speed and said coolant flow to maintain said coolant circuit within a predetermined temperature range.