Audi A 4 B 7 Bleeding Cooling System

So I changed my coolant, waterpump, timing belt etc., and now its time to bleed the system. After the cooling system has been drained, it needs to be filled & bled. a simple way to bleed the system is to pump & hold coolant hoses, which creates a. unscrew the coolant resivour and tilt up to where the coolant input hole is at the highest point. take coolant cap off start car and let warm up After a few minutes you will see bubbles in the coolant return line. (the skinny top one) the black coolant pipe that runs between the intake manifold and the valve cover there is an alan screw The problem with our cars is that the heater core is the highest point in the system, so air will always get trapped there. Doing so will expunge any trapped pockets of air bubbles from the cooling system that can cause overheating.