High performance Race, Drag or Modified Street Cars may benefit from a Water Swirl Pot in the water system. Running a coolant system under pressure and close to the limit may lead to “hot spots” in the water system causing localised “boiling” of the water causing steam and air to develop within the cooling system.
Shown above a typical example of a water swirl pot. If designed and integrated correctly into the system the “pot” will cause the water to “swirl” and spin within the pot. This will allow any potential air or steam in the system to rise to the top and vent back to the header tank (if separate) or in this case rise to the top of the tank away from water flow. Bear in mind in this instance the swirl pot will also aid in dissipating heat away from the water during the “swirl” assisting in reducing water temperatures. Note then it is also important to position the swirl pot in the coolest place possible within the engine bay. Typically it will need mounting between the thermostat (if fitted, or engine water outlet) and the radiator intake to maximise efficiency. If the swirl pot is not integrated as part of the header tank then an air outlet should be welded in the tank at the top and vented back to the main header tank. Intake and outlet (flow pipes) should be large enough to suit the engine water flow and not impede it in any way. The “taller” the swirl pot the more cooling effect and chance for the air to percolate to the top of the tank out of water flow. Remember hot water rises and cold water descends so as the water swirls and cools it naturally flows to the bottom of the tank – similar to your kettle or teapot at home.
Which is why your cup of tea can be warm at the top of the cup and cool at the bottom. Any air in the water system will reduce the amount of heat being transferred as it flows through the fins within the radiator & hence the importance of removing or venting the air back to the header tank or out of the water flow