One or more techniques and/or systems are disclosed for a new coolant tank that may also provide a structural element to the frame of the engine compartment. The coolant tank is comprised of a rear wall that also makes up a portion of the firewall in the engine compartment. A structural coolant tank component is engaged with the rear wall to form the coolant reservoir. The coolant reservoir can provide support to attach structural elements of the vehicle, and can also allow for improved space efficiency in the engine compartment. Further, improved access to the filling port is provided, while continued operation and desired function is maintained even at extreme vehicle tilt.