This weekend I'll be changing the coolant for the first time on my daughter's 2011 Kia Soul w 1.6L engine, it's LONG overdue. I know to do the flush I'll need to drain, refill with water, warm up the engine, then let it cool again to drain and repeat until clear. My question is, how cool do you really need to let it get before you take off the radiator cap? Unless it is piping hot I would think if it's a little hot still it'll just vent as soon as I crack the cap in which case I know not to go further. The reason I'm asking is if I need to drain and fill 3 or 4 times and each time I have to let the engine completely cool off it's going to take a long time (it's already warming up here in Phoenix). I'm curious if I can cut some corners on the cooling of part. I'll also need to make sure I get all the air out really good while I have the car before I give it back to my daughter, I won't have much ability to check up on it too often. Fun story............when I was a kid I saw some folks take the radiator cap off an old pickup truck while it was hot. As soon as that cap let go there was a geyser of steaming water about 8 feet tall. Crazy hillbillies...........lol I still think about that to this day whenever I deal with radiators. And I'm 50.