Yellow Engine Coolant Recovery Tank Cap (54201) by Dorman®. Type: Snap Fit. Material: Polypropylene. Finish: Yellow. Package Type: Box. Length: 4.75″. Width: 2.25″. Dorman offers a variety of Engine Coolant Recovery Tank Caps for a range of applications. All the Engine Coolant Recovery Tank Caps are constructed of high-quality plastic. They effectively protect the cooling system by providing a tight seal against the elements.