I have used this Lisle funnel kit in the past previous radiator work, but it’s not necessary. It’s about $25 and handy when you have to drain the cooling system. It allows you to run while full of coolant and gets all the air bubbles out. I also turned the heater to the highest setting. I let it idle for about 10+ minutes until I stopped seeing air bubbles come up. I squeezed the radiator hoses to help it along. Make sure there are no leaks anywhere. Then I used the residual coolant lef