A4.B5.DIY.Engine.Cooling.BleedCoolingSystem
From QuattroWorld Wiki
Background
Thanks to pac1085 here are the symptoms:
You replace the coolant flange or something else in the middle of the thermostat and the reservoir. You fill up your coolant/water mixture. You then crank your car and it overheats and the thermostat doesnt open. The likely cause of this is air in the cooling system.
You can check if the thermostat is open by touching the lower radiator hose to see if its warm. A warm bottom hose means the thermostat is open. Having the heater working in the cabin will also tell you if it is open. You will need to let the car warm up to check this.
Steps
To bleed the system of air have your car turned OFF. Pull off the left heater core hose (under the accordion cover) to where the bleed hole will allow the air out but the end is still attached to the flange. See below (outlet side).
Completely fill the coolant reservoir and keep it filled through the process otherwise coolant will not enter the crossover pipe. Unscrew the three screws that attach the coolant reservoir. Lift the reservoir in a way that the coolant can enter the metal crossover pipe through the small hose on the side of the reservoir and ensure the reservoir is higher then the bleed hole on the heater core hose. Eventually you will see constant stream of coolant come out of the bleed hole on the outlet hose.
Reattach everything in reverse order and you should now have a bled cooling system.
Dillon (nunya)
