Richie writes: “Air pockets within your auto’s coolant system can cause big problems when its hot out. This tool allows you to painlessly get rid of those pockets without flushing your entire system — unless you’re due for a flush anyway!”
Essentially this funnel snaps into your radiator fill port and slowly/steadily meters in the fluid, giving two advantages: less air in the system, and the ability to fill the whole system in an unattended fashion.
It comes with three different adapters which Lisle claims fit “most domestic and import cars and light trucks.” It retails for $26, but Froogle turns it up for as low as $20. Watch out — many shops sell it for $30 or more!