I've searched on every audi forum I could find and posted questions, I even have the bentley repair manual as well...so any help would be greatly appreciated.

1. the heat just stopped working, well, it blows like 5 degrees warmer from Lo to Hi

2. I have bled the system every way people have told me too, ie, holding the reservoir up, using bleedhole...and when I bled it with car running (cold of course), reservoir open, bleedhole open, liquid flows out fine...same as with holding the reservoir up and bleeding it that way, but there still might be air in it??

3. The hoses on the heater core are both the same temperature when the car is at operating temperature-the are both hot. When it's hot however, and I pull the return off, flow seems very minimal, but people tell me that doesn't indicate anything at all...

4. thermostat opens and closes fine, I notice it in the reservoir and the hoses...

5. top and bottom radiator hoses warm while it is running

6. I hear the temperature flap open and close (I'm slowly starting to think that is it...though)

7. Car does NOT overheat...not losing any coolant...

couple of odd things which may help: I have had the bleed hole open while the car is at operating temperature, and yes I wasn't trying to bleed the system, just dinking around-while the thermostat was opening and closing, some bubbles came out every now and then with air of course, BUT the heater started blowing HOT air a few times....

Also, the temperature gauge, while I'm dinking with it again, sometimes when it's at operating temperature, the indicator drops down to the 'C' again and slowly warms up again, HOWEVER the car has been running for awhile and is warm.

Any ideas?

 

Hi Mark,

I'm having a similiar problem on my '97. Did you find much gunk came out of the heater core when you flushed it?

Having read around online I believe some people have flushed their heater cores with acid/oxyclean with some success. However, I don't know what this would do to the heater core in the long term.

I was wondering how you knew the thermostat opens/closes fine so I could have a look at that on my vehicle?

Thanks

 

Sounds like a blend door issue. Are you 100% positive it's moving? Hearing a motor isn't enough. You need to get under the dash and physically check the linkage to the blend door. If it's not moving, you have no control over the temperature.

 

i would bet money you got a bad t-stat, but not in the way you think. if it failed already and a previous owner put in a failsafe t-stat they stay open and the car takes really long to get the coolant hot (well at least in my old car it did). i would change that out first. start out with the cheap stuff.
on the other hand masterpenguin (spelled properly) brings up a good point. flush that bitch!

 

Eh, re-reading this makes me agree with redline380 to a point. Sounds like a dying t-stat. Although, it can be a real PITA to get all the air out of the coolant systems in these cars. it's why shops use a venturi or automatic coolant replacement setup to keep out air-locks.

What are you doing when this happens?

 

First of all, thanks so much for responding to everyone....this forum ROCKS!!!!

Mastapenguin,

You can tell your tstat is opening like any other car....my temp gauge goes up to the middle, then goes down a little-or you can feel the pressure in your hoses. Like Tweaked said, if your car takes FOREVER to warm up, ie. gauge stays really low close to the 'c' then you don't have a thermostat. I have a chevy with no tstat in it and it NEVER warms up...

Tweaked, yeah, I was thinking it is my tstat because of the 'weird' issue with when the car is running for awhile, and I open the reservoir, yes carefully, the temp gauge goes down to the 'c' again and slowly warms up AGAIN. I'm gonna replace that and flush out my core with oxyclean....however, the hoses under the hood and heater core are very warm when it's running and the temperature stays constand on gauge at middle between 'c' and 'h'...but then again, it could be the tstat as well.

The reason I ALSO think I am NOT getting all the air out, is because when I open the bleed hole when it's at operating temperature (and the flow drops on the return hose), and let it 'bleed' for a while, the heater starts working, so to me that rules out the blend door...right?

I'll have a professional flush it and bleed it soon and see what happens, although, I am stubborn at times, i've bled it every which way the bentley manual says and for some reason, since I'm stubborn, still think there's air in it....

As for the blend door under the dash TWEAKED, is there an 'easy' way to get under there quickly, or do I need to remove the dash the way the bentley manual says.....???

What i'm gonna do is replace tstat, flush heater core with oxyclean, bleed it myself, see if it works, then take it and have someone flush and pressurize it professionally and we'll see.

TWEAKED, let me know about checking the blend door, is there an easy way??

BTW, I did buy this A4 for $300 (yes $300)for my kid, and so far so good, runs great, except for the heater....

Marc

 

redline380, I AM going to replace tstat next week, but if it is bad and has been by passed, why was the heater working properly, then now it doesn't, and wouldn't the temp gauge and car not warm up properly? I'm new to audi's, but have been working on cars my whole life, this german engineering is just weird to me, nothing is simple...lol.....so, since it's all weird, maybe it is the tstat....it was low on coolant when I got it, but how much air can really be in there????

Thanks.

 

Just wanted to post some more info....I drove the damn thing this morning, it was about 34 degrees out, lo and behold, the temp stayed at "C" on the gauge???? then when I stopped at a light, it went up to the first mark, then when I drove again it went back down to the "C"???? So, I'm thinking tstat right?? am I right?? so then, I drive home this afternoon, the temp gauge goes up SLOWER than it has...but at the halfway mark between the "C" and the middle of the gauge, I get blaring HOT heat??then it kept creeping up until it stopped in the middle...but no heat again?? I'm confused here, if it worked at the halfway point between the "C" and middle of the gauge, why would it not blow hot when it rests where it should??

How hard is it really to change the tstat on these things???

thanks again everyone...

 

quick update, maybe this will shed some light on it....i'm back to thinking it's AIR or clogged Heater core (even though I've bled and bled and flushed heater core)....when car is at operating temp, if I leave the climate controls OFF for a few minutes, then turn on the heat, I have hot air/heat for a few minutes then back to cooler air???If I repeat this, I get heat for a little bit.....then none again....hmmmmmm

Thanks.

 

to me it would make sense for it to be the tstat with your updated info. if it were a failsafe tstat, it would stay open making the coolant take a long time to get hot. when you turn the heat on, it blows hot for a while until the coolant cools down from the heat being taken away. if the tstat worked, it would blow hot air, then close and get close to warm up coolant, than open again and the coolant would stay hot.