B8.5 takes way too long to warm up in the winter

[djapeA4]

Hi everyone,

I am a new member here and own 2013 A4 2.0T since last year. Since I bought the car in the winter last year, I don't recall seeing this issue then, or maybe I wasn't paying enough attention. Basically now I'm noticing that it takes up to 22 minutes before the optimum temperature is reached (the middle of the range or 90'C.). This happened the other day even when the outside temp was only -2'C. What I find concerning is that while in traffic during that "warm up' period, the temperature gauge goes up and down multiple times, and usually dips down at the red light to then go back up when the engine revs up a bit while driving. Only when the optimum temp is fully reached, the gauge will stay in the middle and not move up or down.

To me this looks like either a faulty (stuck open) thermostat or the coolant's temp sensor issue. I have read somewhere here a thread where people say that 15-20 min warm up is normal.

This is my first Audi, so it would be nice to hear from the experienced Audi owners if this is normal or not.

Thanks.

[U_know_me]

Hi everyone,

I am a new member here and own 2013 A4 2.0T since last year. Since I bought the car in the winter last year, I don't recall seeing this issue then, or maybe I wasn't paying enough attention. Basically now I'm noticing that it takes up to 22 minutes before the optimum temperature is reached (the middle of the range or 90'C.). This happened the other day even when the outside temp was only -2'C. What I find concerning is that while in traffic during that "warm up' period, the temperature gauge goes up and down multiple times, and usually dips down at the red light to then go back up when the engine revs up a bit while driving. Only when the optimum temp is fully reached, the gauge will stay in the middle and not move up or down.

To me this looks like either a faulty (stuck open) thermostat or the coolant's temp sensor issue. I have read somewhere here a thread where people say that 15-20 min warm up is normal.

This is my first Audi, so it would be nice to hear from the experienced Audi owners if this is normal or not.

Thanks.

At 28 degrees taking 15 to 20 min is about normal maybe a little longer than it should be. The fact that you see it dipping back & forth and going down when not moving, as you mentioned it points to a stuck open thermostat. It could be the temp sensor but that is more rare of a failure.

[djapeA4]

At 28 degrees taking 15 to 20 min is about normal maybe a little longer than it should be. The fact that you see it dipping back & forth and going down when not moving, as you mentioned it points to a stuck open thermostat. It could be the temp sensor but that is more rare of a failure.

Thanks for your input, much appreciated. I just have to show it (temp going up & down) to my dealership "when" it's happens because right now it's intermittent, only happens every other cold start not always. This morning before going to work, no issues, after work it did it again and the temp was +4'C. Maybe the thermostat is just starting to go bad.

[jfo]

Thermostat would be my guess too. If you have access to VCDS, it may show a code if it's the sensor going bad. I haven't tried this, but you could likely enable logging of engine temps, which would show the dealer the activity.

[djapeA4]

Thermostat would be my guess too. If you have access to VCDS, it may show a code if it's the sensor going bad. I haven't tried this, but you could likely enable logging of engine temps, which would show the dealer the activity.

Interesting...except I don't have the VCDS and I am not sure I would mess with that stuff at least until the car is still under warranty (1.5 months). However, considering the level of sophistication in today's cars ECU's, I would expect the dealer should be able to read codes that would indicate that the thermostat is about to go. Usually there are readings that are treated as warnings, before the CEL is finally triggered, right?

[elscotto80]

I have a similar issue where the gauge goes down a little from normal then back up. Took it to my local shop to take a look and they couldn't find anything wrong, they ran some tests on the gauge and sensors. Said to keep an eye on it. I believe there will be a code for temp not reached which would be stored and would not trigger a MIL. I have read and discussed with the shop that it could be the CTS (coolant temp sensor) which can fail. If the thermostat fails in the closed position you will know real quick.

Using VCDS will not in any way affect your warranty. Its a great tool to diagnose issues and do some tweaking to turn on factory options that are disabled in our cars.

[djapeA4]

I have a similar issue where the gauge goes down a little from normal then back up. Took it to my local shop to take a look and they couldn't find anything wrong, they ran some tests on the gauge and sensors. Said to keep an eye on it. I believe there will be a code for temp not reached which would be stored and would not trigger a MIL. I have read and discussed with the shop that it could be the CTS (coolant temp sensor) which can fail. If the thermostat fails in the closed position you will know real quick.

Using VCDS will not in any way affect your warranty. Its a great tool to diagnose issues and do some tweaking to turn on factory options that are disabled in our cars.

It's really nice to see the others with similar issue. Whatever it's causing it, whether it's thermostat or CTS, I want it to be diagnosed so it gets repaired under warranty which will expire soon. I am actually surprised that with the car's low mileage (63,000 km) there would be a need for such repairs. On the other hand I'm fully aware, and have experienced issues with weak thermostats on other German cars. BMWs are pretty bad, my old 99 323i TS failed twice in the same year but the mileage was already 200k.

[djapeA4]

I think I may have discovered a pattern to this behavior. It appears that the temp gauge goes down only in this situation: On a cold day (at around. -8'C or colder) the engine hasn't yet reached it's optimum operating temperature of 90'C, let's say it's 1/4 way up, so obviously as I'm freezing my ass off, I have the air blower & seat heater on high. The moment I stop at the red light, the engine is now idling and the temp gauge starts going down. As soon as am able to add some revs and start driving again, it starts climbing up.

So I tested it today in the same circumstances but my air circulation and seat heaters were off, the gauge was NOT going back down. My conclusion is that this must be the way Audi and other German cars are built since this doesn't happen with any of the Japanese vehicles.

I am still go to see the dealer on Monday just to be sure it's OK.

[twixinthemix]

My 2013 2.0T takes about 2 minutes to blow warm air, and about 1.5 miles to get to ~90C. If you turn the fan on high it will cool your motor down. Leave it at 5 or less.

[van462]

If you have it in auto or defrost likely the A/C system is also on to aid in defrosting. it may be also turning on the front cooling fans drawing more cold air thru the radiator.

[U_know_me]

So I tested it today in the same circumstances but my air circulation and seat heaters were off, the gauge was NOT going back down. My conclusion is that this must be the way Audi and other German cars are built since this doesn't happen with any of the Japanese vehicles.

I am still go to see the dealer on Monday just to be sure it's OK.

I would be willing to bet you it is a stuck open thermostat. That is not normal at all.


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[djapeA4]

I would be willing to bet you it is a stuck open thermostat. That is not normal at all.


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I know, that's what it looks like. Or at least a "sticking" T-stat that only gets worse on colder days.

[djapeA4]

So finally took the car to the dealer and they found one big NOTHING. No fault codes of any kind, so apparently when it's cold outside make sure to turn the fan way down until it reaches 90'C. Because somehow the fan cools the engine down while it's trying to reach it's optimum temp. This has to be something to do with German's design of that system. I believe my old Beemer used to take a very lng time to warm too, so it's probably the same here.

[lettuce]

So finally took the car to the dealer and they found one big NOTHING. No fault codes of any kind, so apparently when it's cold outside make sure to turn the fan way down until it reaches 90'C. Because somehow the fan cools the engine down while it's trying to reach it's optimum temp. This has to be something to do with German's design of that system. I believe my old Beemer used to take a very lng time to warm too, so it's probably the same here.

I mean, pretty much ever car in the world will do this. Here's a shot of my old 86 Monte Carlo to help explain why:



That green dot is where the thermostat is. That opens when the car reaches operating temp to start flowing coolant through the radiator to cool it down. It's closed when the car is cold to warm it up faster. It's there to regulate engine temperature.

Those two hoses that go front to back marked in blue are the hoses that connect the engine to the heater core. Those are hooked up directly to the heater core from the intake manifold and water pump, respectively. They are not controlled by the thermostat and are always open.

Our cars have a similar, albeit more complicated system. The heater core is hooked up to the back of the head and the auxiliary water pump, which is used to provide coolant to the turbo, so is always on when the car's on. No thermostat is involved in this part of the system. You can see the two larger red-capped lines in the left pic here, and where the pump line comes from on the right pic:



And you can see where they enter in through the firewall here, right above the transmission:



By turning on your car's heat, you are essentially using your heater core as a small radiator to sap engine heat out of the coolant and applying it to your car's interior. If the heater system wasn't set up like this, bypassing the thermostat, you wouldn't be able to get heat in your interior until your engine reaches operating temp. It's always a good idea to keep the heat off or very low until your car warms up.

Of course if it never reaches operating temp even with the heat off, or reaches it and has trouble maintaining it, your thermostat is probably stuck open. Like mine was. Luckily I already had to pull the motor out to refill my washer fluid so I just swapped it out while it was on the stand.

[ashtonhess]

I have a 2011 A4, it also takes a while to warm up in cold weather. Because of this, it gets rather annoying when on short trips because i'm always nervous to go anything but really easy because i hear the oil needs to be warm to keep the turbo healthy.

Anyone know anything about temp and turbo health? should i let it warm up all the way every time before doing anything other than really easy acceleration?


Ashton

[Gysty]

Try to do that but turn your a/ compressor off and see what happen. You probably have a thermostat issue. This piece closes the circulation from rad to engine, when engine starts to warm up the thermostat opens slowly, my guess is that the cold coolant inside the rad starts to circulate across the rad to the engine and the warm coolant from engine to rad, and drops the temp inside the engine block, closing the thermostat again, and this makes the gauge to drop as well. You may also need a coolant flush. Another posibility is if you have a coolant leak, i can somehow create an air pocket and that cause false readings on the coolant system.


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[richardm0025]

This happened to me. Audi replaced tstat and water pump and still had the issue. I then decided to flush the coolant system and now warms up in short drives with the heat on full blast.


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[djapeA4]

This happened to me. Audi replaced tstat and water pump and still had the issue. I then decided to flush the coolant system and now warms up in short drives with the heat on full blast.


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Interesting. I might do the same since the car is at just over 60k kilometers. It would be interesting to see if it has something to do with the coolant's chemical properties once it gets old.

Even though some people here tried to lecture me on how the cooling system works (and how most cars today have the exact same system), I feel that there's a slight difference somewhere. Maybe the heat is taken directly from the engine block instead of the coolant, I don't know. There must be a reason for slow warm ups in German cars compared to Hondas, Toyotas which warm up in half time under the same circumstances.

[elscotto80]

Mine warms up pretty quick, but the needle drops below the middle randomly. Heat always works fine and i do not see any overheating symptoms either. Maybe a coolant flush is in order, I have 85K and the only time it was changed was at 25K during oil consumption repairs. I know Audi claims its lifetime fluid, but what are you guys changing it at?

[lettuce]

Even though some people here tried to lecture me on how the cooling system works (and how most cars today have the exact same system), I feel that there's a slight difference somewhere. Maybe the heat is taken directly from the engine block instead of the coolant, I don't know.

lol, yeah. Fuck me for 'trying to lecture' you. You obviously have a much better grasp on automotive HVAC systems than I do.

[Gysty]

Japanese cars have smaller and less complicated coolant system, german cars demands to flush fluids every 2 years, there is a special tool called hydrometer used to check the coolant quality, but even if it says is good, has to be replaced every 2 years or certain amount of miles. For the record, when i said fluids i mean all fluids, especially brake fluid and p/s fluid, they use to absorb humidity and deteriorates with the time causing brakes and or p/s components premature failure, specially abs modules


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[djapeA4]

lol, yeah. Fuck me for 'trying to lecture' you. You obviously have a much better grasp on automotive HVAC systems than I do.

Why don't you then answer the straight questions that I asked (and many others who have stated to have the same issue), instead of posting 4 pics of an old '86 American vehicle that is suppossed to be a model for your explanation of a German car. Riiight, they are all the same! And you're not reading other people's responses either. Someone just said flushing the coolant did the trick. Maybe there is reason why that resolved the issue. It's not always the stuck open thermostat, I already said the dealer confirmed the T-stat was fine as well testing other things and found nothing.



Here

[djapeA4]

Japanese cars have smaller and less complicated coolant system, german cars demands to flush fluids every 2 years, there is a special tool called hydrometer used to check the coolant quality, but even if it says is good, has to be replaced every 2 years or certain amount of miles. For the record, when i said fluids i mean all fluids, especially brake fluid and p/s fluid, they use to absorb humidity and deteriorates with the time causing brakes and or p/s components premature failure, specially abs modules


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Thank you, thank you, thank you - for proving that I wasn't loosing my mind. All of this makes PERFECT sense. I have to flush my coolant!

Thank you sir, you just made my day.

[lettuce]

Why don't you then answer the straight questions that I asked (and many others who have stated to have the same issue), instead of posting 4 pics of an old '86 American vehicle that is suppossed to be a model for your explanation of a German car. Riiight, they are all the same! And you're not reading other people's responses either. Someone just said flushing the coolant did the trick. Maybe there is reason why that resolved the issue. It's not always the stuck open thermostat, I already said the dealer confirmed the T-stat was fine as well testing other things and found nothing.

The first picture I posted was of my old Monte Carlo to show you a simplified example of how car HVAC systems work. The other 3 pictures I posted are of my personal B8 A4 with its engine out in my garage and of one of its spare engines I have on a stand to show you the exact cooling and HVAC system being discussed. They are functionally the exact same system, I just thought it would be easier for you to understand if I used a less complicated system initially to illustrate how they work before seguing into our slightly more involved system.

I had a stuck open thermostat on my A4. The car threw no codes and had no other symptoms other than taking too long to reach operating temp, during which time it ran rich, and having difficulty maintaining temp once it did warm up. When replacing the pump I found that the thermostat was stuck open by about a half inch. No way to diagnose that without removing the pump, or I suppose pulling the radiator hose off when the car's cold to see if it sprays coolant everywhere if you don't mind making a giant mess. Make sure your cat's not in the garage with you if you choose to go that route.

[djapeA4]

The first picture I posted was of my old Monte Carlo to show you a simplified example of how car HVAC systems work. The other 3 pictures I posted are of my personal B8 A4 with its engine out in my garage and of one of its spare engines I have on a stand to show you the exact cooling and HVAC system being discussed. They are functionally the exact same system, I just thought it would be easier for you to understand if I used a less complicated system initially to illustrate how they work before seguing into our slightly more involved system.

I had a stuck open thermostat on my A4. The car threw no codes and had no other symptoms other than taking too long to reach operating temp, during which time it ran rich, and having difficulty maintaining temp once it did warm up. When replacing the pump I found that the thermostat was stuck open by about a half inch. No way to diagnose that without removing the pump, or I suppose pulling the radiator hose off when the car's cold to see if it sprays coolant everywhere if you don't mind making a giant mess. Make sure your cat's not in the garage with you if you choose to go that route.

So when you had these symptoms of either not reaching the optimum temp, or once reached, it couldn't be maintained, - was this happening only in the very cold weather, but also when it's relatively warmer outside?

In my case it's only happening on days like -10'C and colder (which we have plenty of here).

And BTW I appreciate your input, you seem to be very knowledgeable about the issue. I was just a bit taken aback with your example and wasn't sure why I was seeing the entire engine removed where you said you had take it off in order to refill your washer fluid?? This had to be a joke, right?

Anyhow, I think I will definitely replace my coolant before next winter, then wait for cold days and see. If it starts happening again, then your diagnosis is probably correct.

[lettuce]

So when you had these symptoms of either not reaching the optimum temp, or once reached, it couldn't be maintained, - was this happening only in the very cold weather, but also when it's relatively warmer outside?

In my case it's only happening on days like -10'C and colder (which we have plenty of here).

And BTW I appreciate your input, you seem to be very knowledgeable about the issue. I was just a bit taken aback with your example and wasn't sure why I was seeing the entire engine removed where you said you had take it off in order to refill your washer fluid?? This had to be a joke, right?

Anyhow, I think I will definitely replace my coolant before next winter, then wait for cold days and see. If it starts happening again, then your diagnosis is probably correct.

Yes, the washer fluid thing was a joke. I replaced my motor for other reasons. When I had this issue I was noticing it taking slightly longer to warm up in the fall with temps around 5C, then got worse until the winter in -10 to -15C weather where it would never reach temp. I'm not saying it's a stuck thermostat in your case, in fact I'm saying it's probably normal, but that's what my car was doing when I had the issue. Even with my heat off it'd never reach temp. Also for comparison, now with the new pump and thermostat it still takes maybe twice as long to warm up if I have the heat on full blast.

Coolant flush certainly won't hurt to try, just make sure you use the right stuff (G13).

[twixinthemix]

just make sure you use the right stuff (G13).

I had a G12+ bottle that was sitting in the trunk of my B5.5 from before I bought it. I had never touched the stuff before so I had no idea what it was supposed to look/smell like. I had to refill some coolant after burping my lines(always had cold heat at idle and never bothered to figure out why before this). It turns out I put about half a quart of MOTOR OIL into my reservoir. Thankfully I noticed the same day and had enough coolant in the reservoir to not tap into the oil. I was able to remove the reservoir and clean it out without getting any into my cooling system. I'm never trusting random bottles included with cars ever again.