sullyj

Winter is rapidly approaching and interior heat is not working. Just had coolant replaced yesterday because of a faulty oil cooler (found oil in coolant overflow tank). Heater control valve replaced by Audi tech to no avail. He now tells me issue may be with motor flaps that control flow to dash outlets.Engine temperature gauge registers solidly in the middle after car warms up. Last winter I had very lukewarm heat coming from driver side dashboard outlet only which got me through winter months. I could only get lukewarm air out of that outlet while car was moving...nothing much happened while at a standstill. No issues this summer with A/C. Car has 180,000 miles which are mostly highway miles, but I'm tiring of throwing $1000 to $1500 at car every other month. Just did total front end suspension job (upper and lower control arms and tie rods) and the oil cooler replacement which all hit me for $3750.00 so you can see at just about at the end of my love affair with Audi's. After reading up on issue it seems the heater core is a possibility. How expensive is replacement? Any suggestions here because I can't see myself driving around with no heat this winter. Never had a car so over-engineered and problematic on simple issues like having heat in the winter. Suggestions?

dvs_dave

Get it hooked up to VCDS diagnostics and see what error codes are coming up for the HVAC. It’s very good at identifying if there are any stuck or malfunctioning flaps/actuators.

If nothing comes up then you need to look into more basic stuff. Has the cooling system been bled properly? Are you sure the heater valve assembly is installed correctly and functioning? Can you feel hot water/cool water circulation when touching the heater core pipes? Etc...standard automotive diagnostics.

As far as German luxury cars go the A8 is no more or less complex than its contemporaries. I would say though that on the most part they are well built and engineered and much less prone to major problems than rivals. And the problems they do generally suffer are well understood and usually pretty simple and inexpensive to fix. And if you’re not very DIY savvy, then you NEED to find a mechanic who knows these cars and their foibles well. Way too many “European specialists” just don’t have the the experience with A8’s to be good at diagnosing them. A8’s are pretty rare compared to s-class and 7-series which is usually what these guys are good with.

2004A8L

My friend's car had some heat then no heat at all, last weekend i ended up draining the coolant and doing a flush on both heater cores some **** came out. .... now there's heat again passenger side is super hot driver side not bad could be better but it's 10 x better then 0 heat lol

sullyj

Is the flap/actuator issue an expensive one?

2004A8L

Last winter I had very lukewarm heat coming from driver side dashboard outlet only which got me through winter months. I could only get lukewarm air out of that outlet while car was moving...nothing much happened while at a standstill.


There's your clue clogged up heater cores

sullyj

Is this an expensive repair?

dvs_dave

There’s many of them, so it depends on which it is, and it’s consequent location. Parts aren’t expensive, but the labor to get to it could be....

ltooz_a6_a8_q7

Before I spend any more money on the car, make sure the valve the let the hot water going into the heater core, simple test, turn on the Heat to HI, turn on the ECON mode = NO AC, go the front of the car, there are 2 lines going into the heater core - If I'm not mistaken - those have bleeder valves on it also. I haven't been looking at this for a long time, and I never had the problem. Hot line from the engine comes in, one line goes out, if both lines are hot, then the core should be OK. It's the same test as if the thermostat opened or closed.
I don't know about the east coast cars, but all my years of owning cars, never seen a clogged core heater ever. Also, if you want to be sure, disconnect both lines, force water in one and should see it come out the other (I'm not sure if this work with Audi but others yes).
Yes, the flap/actuator could be a problem. Read this long POST to see if it's similar.
Again, read all the posts before assuming anything. This is what one had replaced.
Cheers,
Louis

2004A8L

Biggest expense was the coolant from dealer $24.89 and two hose connectors at $ 2.99

I do not know how much someone would charge for it or if dealers does it..

dvs_dave

There’s actually 2 heater cores. Left and right. So there’s 2 main hot/cold lines to the heater control valve assembly, and then from there another two pairs of hot/cold lines leading to the two actual heater cores. So you need to check 3 hot and 3 cold lines to do a full diagnosis of the heating system water circuit flow.