I followed the advice of some good people here and it is.
Disconnect both heater hoses.
use a garden hose to chase out any loose debris.
Get 2 pieces of 3/4 " hose point the both and use a funnel to fill the heater core with UNDILUTED CLR.
Let it sit overnight.
Flush it out again with the garden hose and blow it out with compress air but not over 15# of pressure.
Your going to be surprised how much crap is in there.
Reconnect the heater hoses.
Top off the expansion tank with G12 / 13.
DO NOT USE THE GREEN STUFF.
70/30 mix.
Run it until it is in the normal mid-scale range on the temp gauge.
Get someone to help to hold the rpm at 2000 and bleed the air out at the heater hose.
It may take a few times to get it all, but it worked for me.

 

HEAT! I have HEAT!!

 

I have the same problem with no heat from my 2002 A4 1.8T quattro. How much would it cost to replace the heater core by a dealer or non-dealer auto-shop, anyone?

 

why dont u just flush the core like others have done and save yourself a 3 to 5 hundred dollar bill. . . . if it does not work then at least u know u have exausted your options before forking out some mula!?!?

 

If you are at all mechanically inclined it is not that tough of a job technically, just uncomfortable from a sitting upside down on your head in the drivers footwell.

Here is the DIY link: B6 A4 Heater Core DIY

Good luck!

 

Its not the fact that its a tough job its the point of not spending money if you dont have too. I would much rather flush the core and save myself the $$$ for the core. let alone the time and pain of installing.

 

Ok, I don't mean to be hijacking this thread but I am experiencing the same issue. the heat issues with my B6 has been a never engine war. This summer I replaced the heater core due, probably the only easy thing to do on this car, took me may be 20 min tops...
Anyhow, does anyone has a good explanation on how to exactly bleed the damn heater core? and how long will it take? How many gallons of coolant with be needed?
Here is my problem, last night I had my brother keep the rpms at 2K and he said the car was making good heat. At the same time I had the heater core hose pulled back and there was no coolant coming out of it what so ever... after about 5 min of reving the engine 2K the heat was great but still no coolant coming out of the hole??? Once he let of the gas and engine was again at idle i noticed a nice steady stream of coolant coming out of the hole (am I the only one who things this design is just obsolete??? I mean you have coolant literally spray all over the place with no control what so ever, its probably just another space engineering designs from audi ) but within seconds my brother said the heat diapered again, yet I had coolant literally shooting out of the hole but no heat??? So i had him get the rpms again up to 2000 and withing a minute or so the heat came back, but no coolant coming out of the hole but great heat in the car? again for about 5 min or so no coolant from the hole but amazing heat? as soon as he lets of the gas pedal coolant starts coming out of the hole and heat goes away? We spend almost 2 hours trying to bleed this thing, at the end with the rpms above 2k and hot heat from the vents and no coolant out of the hole I end up pushing the hose back all the way in put the clamp back on it, we parked the car outside and let it run at idle while were cleaning the mess of coolant all over the garage floor, again thanks to the brilliant engineering design by Audi
About 15 min latter the heat was still good in the car and coolant level was perfect. On my drive back to town, I have a garage about 3-4 miles outside city limits, the heat was great. I drive at a steady speed of about 50ish and the rpms never really passed 3k under acceleration... as soon as we got back to town the heat slowly disappeared again , in town i did get the about 3-4k and but again the heat came really weak???
So back to the original question? Am I doing something wrong? I have probably wasted close to 3+ gallons of coolant trying to bleed this heater core and this is the 3rd time we are doing this exrecsice, not that I have nothing better do to in literally subzero temperatures here in NW Ohio ... its getting really annoying at this point and I am getting really frustrated with this car...

 

well i never replaced the whole core but when i bled the system i would let the car warm up all the way turn it off and just open the coolant cap. And let it burp the system. I did that about 5 to 8 times until it stopped gurggling

 

couple thoughts

Any chance you have the heater core hoses swapped between in and out? if you have coolant coming out the hole then it is burped.

when there is no coolant coming out the hole with RPMs up can you hear if it is pulling in air? that isn't helping you at all and creating more problems if that the case.

Like pa4ul said, usually just needs a few heat and cool cycles to fully burp. Once or twice at heater core, a couple times at the bleeder hole and other than that at the coolant cap.

only other thing is how old is your water pump? Could be a weak waterpump impeller starting to slip so only making enough system pressure during higher RPM.

Good luck

 

timing belt kit is 2000 miles old... new metal impeller water pump, new t-stat, new coolant flange (back of the head) no coolant leaks. I am not sure having a couple of coolant cycles is the proper way of bedding the coolant system. The heater core is new, installed this summer. Its impossible to swap the hoses on the heater core... May be I just need to suck it up, buy more coolant, which will spill on the floor anyhow and continue to bleed the coolant system...
No one really has a logical explanation of to why this is happening...