Patent ID: 8397681

Claim:
An engine coolant system for a vehicle, the engine coolant system having a minimum desired coolant fill level, and the coolant system comprising: an engine cooling system having a minimum desired Coolant Fill Level; an expansion tank for the cooling system using a liquid coolant; a tank body of the expansion tank defining a first volume containing coolant and defining an upper volume of air; wherein the tank body defines a continuous volume at least a portion of which extends above and below the Coolant Fill Level; a coolant outlet to communicate coolant away from the tank body; a coolant inlet to communicate coolant into the tank body; a bladder defining a second volume containing air within the bladder, wherein the bladder includes a flexible membrane moveable between a first position to decrease the second volume and increase the upper volume, and a second position to increase the second volume and decrease the upper volume, wherein the upper volume of air is located within the tank body at a different location than the first volume of coolant and the second volume of air, wherein the upper volume of air is in fluid communication with the second volume of air; an actuator for selectively controlling the membrane movement between the first and second position to maintain the coolant at a level above the Coolant Fill Level during operation of the vehicle; and a communication line in fluid communication between the upper volume and the second volume.