A coolant control system of a vehicle includes a pump control module and a coolant valve control module. The pump control module selectively activates a coolant pump. The coolant pump pumps coolant into coolant channels formed in an integrated exhaust manifold (IEM) of an engine. The coolant valve control module selectively actuates a coolant valve that controls coolant flow from the coolant channels formed in the IEM to a transmission heat exchanger based on a first temperature of a transmission and a second temperature of coolant within the integrated exhaust manifold of the engine.