Hello everyone. So I have an 2008 Audi A3 with the 2.0T gas engine with around 95200 miles. Recently starting last Friday (11/14/14), I've been having a problem with my coolant temperature gauge and coolant level warning indicator. The first time I noticed it was on Friday night when driving home from work. About 5 minutes in, I turned the hot air on to warm up and it felt like it always did. I then looked down at the dash board and saw that the temperature gauge didn't move at all. It was stuck at 0. I drove around a bit to make sure that the engine should have been warmed up at that point (around 10 additional minutes) and still noting. The air coming from the car felt still felt warm though, again like nothing was wrong. The outside temperature when I started my car that night was around 32 degrees Fahrenheit.

The next morning on Saturday when I started my car, the warning to add coolant came on. I checked the coolant level and it looked like it was normal (it was at the point in the overflow bowl where the bowl bulges out which from the book, it looks like that is the indicator for the max coolant level. And it was above the min line. I didn't have the right coolant to top it off so I just ignored it and assumed the sensor was bad. Then when I drove for like 30 seconds, the warning went away. Temperature that morning was also around 32 degrees Fahrenheit. I did drive around a bit on Saturday and paid attention to the temperature gauge and saw it didn't move still. The air was still blowing out warm though. I did more driving on Sunday, quite a bit and then suddenly I saw the temperature gauge was working again. Though I noticed that it didn't go up to where is used to (right in the middle of the gauge.) Ever since, the temperature gauge has been partially working. It doesn’t hit the middle but it goes from a little over the white line between the 0 and middle lines to almost the middle and goes between the two. The add coolant warning also comes on right in the morning when the car is cold and I check it every time and its the same. The only time it didn't come on was on Thursday (11/20/14). I was off work then so I started the car later in the day and the temperature was around 43 degrees Fahrenheit.

So basically it seems that the warning to add coolant will only come on when I first start the car in the morning when its really cold out (32 degrees) and goes away quickly when starting to drive. Once the car is warm, the warning won't come on when shutting off and starting again. In the afternoon, sometimes it comes on depending on the temperature I've noticed. If the car says its around 30-35, it comes on and if its above, it won't. As far as the coolant temperature gauge, its been doing the same thing since it started partially working again.

From the research I've done so far, the coolant temperature gauge problem could be caused by the coolant temperature sensor going bad or being bad or by the thermostat starting to go bad. (Apparently if the car detects its not warming up as it thinks it should, then it disables the gauge). And I guess that could be caused by if the thermostat was going bad. Either not opening at all or always being open or opening too quickly? (I assume its not stuck open cause the car heats up and it probably wouldn't at all with this cold out. I haven't gotten an overheating engine warning so I guess its not stuck closed either?) These are the only things I've found. I'm not sure if there is anything else that could be the problem. And oddly enough, this only started to happen when it got really cold out. The night before last Friday and before, neither of these problems happened and from what I've noticed, it wasn't as cold out either in the morning or afternoons. I've only had this car since April this year (when it was warm), so I've never had the car when it was this cold out. So I'm also thinking at the same time, maybe the cold is just messing with the car? But its probably a bit beyond that. What do you guys think? Any help is appreciated in advance.

And if it is the sensor or thermostat, where is the best place to get the parts? And as far as coolant, the book says that I need G12+ type and apparently that’s only sold at Audi/Volkswagen dealers?

 

Sounds like you did some good research there. I would also replace the temp sensor(s) first. If that doesn't fix it - replace the thermostat. Remember that if you throw a check engine light because of the temp gauge you have to clear it or the temp gauge will remain dead even after replacing sensors.

As for the coolant level sensor - those things are horrible. My wife also started throwing a code during the summer because it was too "low". However it was spot on at the MAX mark. According to several articles I found it seems a little picky (or maybe going bad) and you have to fill it up above the MAX mark. I did and had no errors since. Sooner or later I probably have to replace it.

To answer your last question: I found my local dealer to be pretty cheap for the G12 coolant so I buy it there rather than online however the difference is marginal. Good advise - never mix it with any other coolant (like Prestone that mixes with all colors!). This (G12) Coolant does not mix well and can cause all kinds of issues (up to clogged radiator).

I like to buy my parts either at ECSTuning.com or genuineaudiparts.com. The first has top notch parts matching (so if you select the right car - you always see the right parts for your model) while the later is usually cheaper but the search option is not the best and confusing.

 

Alright thanks. Yeah the coolant sensor gave a warning when I turned my car on this morning from my house. My driveway is slanted down. But when I started my car in the afternoon at work, it didn't come on. The ground was flat there so I'm not gonna worry about it right now lol. Temperature was around 32 each time as well. Though apparently replacing the sensor causes coolant to leak out so I'm gonna buy some anyway. Yeah' I've been reading about the coolant and will just buy it at the dealer like you and others have said. And I'll check those sites out for the part, thanks! A few more things I've noticed as well. It seems like the car isn't making as much heat as before? Though I just may be remembering wrong and paranoia is causing me to think there is something wrong when there isn't lol. And this has been going on for a week. Is this gonna damage the engine if the repair is prolonged to long?

 

As long as your engine is not overheating I don't see it causing long term effects. Right now it sounds more like the engine is either not reaching optimum temperature or not fast enough. Both are basically emission related issues (+possible lower mpg) but overall you should be safe to order the parts online while continuing to drive until you can fix it.
However if the gauge is disabled and the computer is ignoring that input - you might not get a notification about the engine overheating - so be careful and keep an eye on everything else (like smoke coming from underneath your hood - BAD SIGN! :P ).

 

Yeah, the gauge was disabled for about a day and half and then it started partially working again like I was explaining before. I replaced a sensor but the problem still persists. Not sure if I got the right sensor but I'm pretty sure it was related to the coolant system. When I took it out, a bit of coolant did pour out. It was a gray, 2 pin sensor. If your looking at the front of the car, its on the right side of the engine and a bit under the engine cover. Easy to see and get too if you remove the battery. So I guess my car must have 2 sensors then. Or the thermostat is really just bad and needs to be replaced -_-. Sigh, I have a feeling thats gonna be it. Well anyways, do you know how I can find out if my car has a second coolant monitoring sensor/where its located? Much easier to try this instead of the thermostat I would think. And yeah, I think the car has another warning light if the car is overheating? Gonna double check. Otherwise no signs of overheating and no check engine light this whole time.

 

Running into a similar issue and I've been searching the forums for some additional symptoms that I'm seeing, any of this sound similar:

First indication was a check engine light and a stuck temp gauge. Took the car home, ran a VAG check and no error codes across the board. Disconnected the battery to reset, engine light went out and gauge started working properly.

Since then the gauge has stopped 2 more times, again no error code and a simple battery reset fixes the issue. I've monitored oil temp and performance and all looks good while driving.

The check light could have been from a loose o-ring on the dip-stick which has caused a small air leak before (I had checked oil the same day) but the lack of error codes is what's throwing me on this. I would expect to see a code for the temp sensor or something temp related.

Did any of you run code checks before changing your sensor or Thermostat? Thanks for the feed back

 

Sorry - no codes on mine. It was only a warning that the fluid is low (even though it wasn't). Topping it of over MAX fixed it for me. Car has been running fine.
The OP however did have the issue you described - so he might have ad some codes, not sure.

Why don't you clear all the codes in VAG-COM instead of disconnecting the battery? Did you run a full scan or just the CEL check?

 

Sheldon - there were no codes to clear, but yes I tried running through the clear process anyhow, then re-tested and still had the same issue. Only cycling the battery fixed it.

 

Are you using a Vag-COM or some generic OBD2 scanner?

If cycling the battery works - it's because it clears some kind of code or module. A proper VAG tool (like the one from Ross-Tech) should be able to clear that as well. Also if the thermostat is the problem and the you keep the temp-gauge "disabled" it should eventually throw a check engine light code.

 

I'm using the V-Checker from ECS Tuning. For the amount of work I do it suffices. Couldn't justify the Ross VAG with the wife. With the V-Checker I ran through all of the control modules but no codes present. I'm aware that the battery is resetting something given that it works but unsure what.

I hear you on not resetting to see if a light comes on. But interestingly enough it may not work (at least within 3+ hrs). The last time it happened I was driving home from out of town and I couldn't stop to deal with it for over 120mi. Never got a light. Maybe it takes considerably longer.