Coolant Expansion Tank (20-0270-01) by Radium. The Radium Engineering tank also has a swirl feature, as shown. Pressurized coolant is sent into the vortex chamber's inlet tangentially and accelerated to a high rate of rotation. This is an old hot rod trick to help aid in deaerating the system. To keep your engine cool and improve your vehicle's performance, this product is just the right solution. Manufactured from high-quality materials, it will surely provide excellent performance and years of trouble-free service.