interconnecting a fluid interchange apparatus with a power steering system of a vehicle ; pumping spent fluid from the power steering system into a fluid receiving container to compress air pressure therein ; interconnecting , with a pressure actuated valve , the fluid receiving container and a replacement fluid container , the replacement fluid container holding a replacement fluid ; automatically opening the pressure actuated valve when a selected amount of the spent fluid from the power steering system is transferred into the fluid receiving container resulting in an air pressure sufficient to open the pressure actuated valve ; and draining , under the force of the sufficient air pressure , the replacement fluid from the replacement fluid container into the power steering system to replace the spent fluid in the power steering system with the replacement fluid .