QSB4.5 Cummins Expansion Tank 3917968 Parts Catalog Ref No. Part Name Part No. Required 1 Expansion Tank 3917968 1 2 Filler Cap 3907022 1 3 Pipe Plug S910B 1 Above is the introduction of the 3917968 Cummins Expansion Tank, while if you need Expansion Tank 3917968, complete Cummins engine or other Cummins product, please further consult our sales.