Hey all!

So, noticed the heat in our 1999 A6 Avant 2.8 was getting pretty weak. Finally today (when its -16 in Parker Colorado), it barely heated up enough to defrost the windshield.

Went to Autozone and got some coolant flush and new coolant. Drained everything. Unhooked the hoses at the heater core and ran compressed air thru both ends. Nothing came out besides coolant, and plenty of pressure.

Did the flush, and for the first time since we bought the car, the temp gauge moved straight up.

Drained it, put fresh stuff in. And fired it up. No heat. I unhooked one of the hoses to the core, started the car again, and nothing is coming out. Swapped hoses and still nothing.

So, what would cause coolant to not come out of either hose from the engine?? Please tell me isn't not the thermostat...

The car runs fine. Doesn't get "hot" as far as the gauge goes.

Didn't "bleed" the system. Figured if the hoses at the core were undone, that would do a pretty good job getting air pushed out. But no coolant was behind it to do that....

Thanks guys!!

 

After unhooking the hoses from the heater core you are introducing air into the system. It should be bled in order to ensure all air is out of the system. Additionally, as far as your initial complaint, this could be a thermostat that is stuck closed thus preventing flow, or a bad water pump. Do you feel a difference between the top and the bottom radiator hoses in terms of temperature?

 

Yeah, trying to figure out how to bleed it. And the hoses weren't hot or cold. One was "full" and one felt empty like it was sucking air...

 

Well, I HAVE HEAT! But now the car won't idle...! My basic Vag-com skills show a 17953 fault for malfunctioning throttle valve... but I didn't touch any of that!

I can clear the fault, and the engine revs up for 2-3 seconds. Then dies down again. I can actually make the engine rev up and down just by hitting the "clear codes" button repeatedly...

Anyway, pulled the ECU, and the battery (just in case). Will plug it all back in and see what happens...

 

Used vcom to reset throttle body. All good now.