Running Hot

Johnny Dart said
In a normal system,the top part of the radiator is called an expansion tank.
The purpose of the tank is to provide space for the Coolant to expand when it gets hot. If you fill the tank to the top of the neck,it will have nowhere to expand when it gets hot,except out the overflow hose and onto the ground.

Not trying to pick a fight,but the proper level of coolant is just above the top row of cooling fins. If you really want to get the absolute most coolant in your radiator,fill it to the top and let the coolant puke out the overflow hose onto the ground.
Keep driving the car,and eventually it will stop,and theres your level.

TrailBeast said
Exactly.
That's why I like to let it purge what it does'nt need instead of possibly cutting it short from the start.

Somebody's in a fight? Who, where?:D

XS3 ....i fill it to the top and let the system decide . it will stop puking when it is happy with coolant level. and just to add, even with the 100+ degree days we have had, i still run 80% water and 20% coolant because i have seen some nasty rusty engines that have ran straight water for long periods of time. i have a fan shroud, a 7 blade fan ,26" 2 core radiator 180* thermostat , my fan sits 1" away from the radiator , i can sit all day in traffic. when i shut my car off after running for an hour or two, my top hose is rock hard (lol) and nothing leaks, not even a hiss.