This disclosure details thermal management systems with two or more cooling loops for thermally managing multiple components of an electrified vehicle. An exemplary thermal management system may include a deaeration device that is fluidly connected to two or more cooling loops (e.g., a traction battery pack loop, a power electronics loop, etc.). The deaeration device is configured to allow for deaeration of the two or more cooling loops while reducing coolant transfer and heat transfer between the two or more cooling loops.