A diesel engine fluid reservoir system having a reservoir of diesel exhaust fluid in thermal communication with a heating element, a first conduit for the flow of engine coolant fluid to the heating element, a temperature sensor disposed to sense ambient temperature and/or a temperature of the diesel exhaust fluid, a controller communicatively coupled to the temperature sensor and communicatively coupled to a sprung gate valve included in the first conduit. The gate valve has a no-flow position and a flow position for control of the flow of engine coolant and includes an endless elastic band sandwiched between a first gate member and a second gate member each defining an opening therethrough alignable with the first conduit in the flow position. In response to a sensed temperature at which the diesel exhaust fluid is frozen, the controller signals the gate valve to be in the flow position.