I have a 03 A-4 with 60,000 miles manual shift . No heat . I had added some coolant to the system and was bleeding the system at the heater core and was getting nothing so pulled the hoses off and no coolant was coming out of any hoses going to the heater core . I had the heater on high . I was thinking the feed hose came right off the thermostat housing without any valves or anything in the line . I am thinking weak water pump .. The 03 runs good and no over heating problems .. What am I missing ?? Thanks .. I work on Corvettes I call this 03 a science project ,love the thing but what a pain to work on .. Thanks for any help..

 

This is a little after the fact but fixed it and don't ask me how .I don't know . What I did was replaced the thermostat with the housing and all the hoses ,flushed out the heater core and bleed the thing 10 times nothing so gave up and a few days later heat and has been working ever scene ?? OK

 

Wow, would guess the thermostat and the bleeding probably did it for you.