No coolant flowing to the heater core.

[B5(02)S4]

I'll start off by saying I'm new to the s4 and new here. I did search and couldn't find anything. I have a 2002 s4 and the heat doesn't work. done a lot of searching and found a few possible causes. Either the heater core is plugged, air pocket in the heater core and coolant system needs bled or the door in the heater box. I started with the simplest one and I am getting no coolant at all to the heater core. The operating temp is great. Warms up and no overheating. I'm completely lost cause I can't figure this one out. Any help would be appreciated.

[zillarob]

Plugged core like all the others.
Backflush with something like clr and should get you through the winter.

[eagano]

I was in the same situation, and didn't think it was a plugged heater core. Of course, it was.

There is some good info in a this recent thread.

[JJ.]

Try bleeding it first, pull back the hose with the hole in it which is going into the heater core (left one), until the hole isn't covered anymore.
Unbolt the expansion tank and lift it as high as possible, with of course the engine running, wait until coolant comes out of the hole in the hose.

I had to do this everytime to get the air out of the heater core and get heat inside.

[B5(02)S4]

Ok thanks guys. I'll flush it just to be sure and then lift the expansion tank. Like I said I'm new to these. But is there like a heater control valve on these? Might be a dumb question but on other cars there are and didn't know if there was one it wasn't lettong coolant get to the core.

[chaos2984]

no heater control valve. And Just flush it out. Take the garden hose to it and flush it both ways. If you cant get the hose to the heater core take the heater core coolant lines off the engine side and you should be able to flush that way. You should see dirty stuff come out and then clear water. Just go both ways back and forth and make sure its clear water each way and you know your done.