Function and purpose - A coolant reservoir is part of the engine cooling system and is a small plastic container attached to the radiator or engine block. Its main function is to collect and store excess coolant that expands when heated, helping regulate coolant levels and system pressure. If your car shows engine overheating, low coolant levels, leaks, or coolant odor, you may need to replace the reservoir. Replacement part numbers - 603278, 603278, CV6Z8A080C, CV6Z8A080B - Please check the detailed description or enter Year/Make/Model to check compatibility before purchasing this radiator overflow tank. Compatible with select Ford models - 2013-2016 Ford Escape L4 2.0L - 2013-2016 Ford Escape L4 2.5L - 2013-2018 Ford Focus L4 2.0L - 2017-2018 Ford Focus L4 2.3L - 2014-2022 Ford Transit Connect L4 2.5L Direct replacement and installation notes - Direct replacement: perfect match, direct replacement. - Replacement procedure: When replacing the coolant overflow tank, turn off the car and wait for the tank to cool down before proceeding. - Material and quality: This coolant reservoir replacement is made from premium materials to ensure superior quality and longlasting performance. - Part type: This is not a genuine part, but an aftermarket replacement.