Volkswagen Repair: Jetta overheating, upper radiator hose, air bubble

Question
I have a 2003 Jetta with a 2.0 engine. One day it overheated and it does it everytime I run it now. When it's running hot it blows cold air from the heater. The upper radiator hose is hot but the bottom one is cold. Is there a way to test the water pump with taking it out?

Thanks


Answer
Hi John;
There is an air bubble inside the cooling system, and it seems to located in the heater core.  You need to evacuate, and refill the system with fresh coolant.  The tool for this is called "Air-lift," and requires shop air at a pressure of 100 psi or better to operate.