# Temp sensor or thermostat



## davidf1 (Jun 10, 2013)

I have got a mk2 TT,I have noticed that sometimes the temp gauge does not get to 90.And when it does it will drop t around 70,the car itself seems to be running ok,even on a cold start or after starting after a good motorway run.now could this be a temp sensor that needs replacing,or could it be the thermostat.I don't have a vagcom.Is there any way I could figure out what it is.Or maybe change the sensor first anyway,as it's the cheapest option,and easy to do.


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## HarboroughTT (Oct 18, 2016)

Does your car get to 90degrees if you are sat in traffic? I had this issue not long back, the car would never quite get to the correct temperature unless in traffic. Mine was the thermostat, got a mobile mechanic to change it out and now it sits bang at 90. Just make sure you have spare coolant when changing the thermostat as he lost around 3 litres when changing it.


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## Hoggy (May 8, 2002)

Hi, As above, more than likely the stat.
Hoggy.


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## davidf1 (Jun 10, 2013)

Ok,what is the item code for the Audi thermostat I need for my car.(2008)model.2.0 l
Thankyou


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## Hoggy (May 8, 2002)

davidf1 said:


> Ok,what is the item code for the Audi thermostat I need for my car.(2008)model.2.0 l
> Thankyou


Hi, I answer your same question on the 23 Dec :roll: :? 
Hoggy.


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## davidf1 (Jun 10, 2013)

How would I be able to tell conclusively that it is the thermostat and not the sensor.When I went to work today the temp gauge never went above 70,and the same when coming home.The car seems to be running ok though.


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## Hoggy (May 8, 2002)

davidf1 said:


> How would I be able to tell conclusively that it is the thermostat and not the sensor.When I went to work today the temp gauge never went above 70,and the same when coming home.The car seems to be running ok though.


Hi, If coolant temp rises when hot engine left running while stationary/in traffic etc. AirCon off, then almost certainly the stat.
Hoggy.


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## poder (Mar 18, 2015)

Feel the coolant hoses to and from the radiator. If they are hot even though the engine has not reached running temperature, it means that the thermostat has opened too early. This is likely the case. If this happens early from cold, you know that the thermostat is at fault as it probably doesn't seal correctly at all. If the hoses don't get hot until the engine has a higher temperature, you have to measure the coolant temperature in an alternative way to compare or get the resistance specs for the sensor and test that separately.


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## Sean02409 (Jan 11, 2016)

Recently just replaced the stat, had very similar problems that you've just highlighted.

I experienced a loss of power, loss of mpg and the heaters never blew out hot air.
Most issues I've read about point towards the actual stat itself and not the sensor.


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## davidf1 (Jun 10, 2013)

I am not experiencing any loss of power.And heating works in the car,but the temp gauge only goes to 70 if that some days,sometimes if in traffic or driving slower it goes up a little.is this definitely a thermostat,and not sensor.


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## Hoggy (May 8, 2002)

davidf1 said:


> I am not experiencing any loss of power.And heating works in the car,but the temp gauge only goes to 70 if that some days,sometimes if in traffic or driving slower it goes up a little.is this definitely a thermostat,and not sensor.


Hi, More than likely the stat...... I'm sure there is an echo in here :lol: :lol: :wink: 
Replace the sensor first then, cheaper & easier.
Hoggy.


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## davidf1 (Jun 10, 2013)

Hi boggy,the car takes a while to warm up on the temp gauge before rising.


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## Hoggy (May 8, 2002)

davidf1 said:


> Hi boggy,the car takes a while to warm up on the temp gauge before rising.


Hi, Only way to be sure if stat or sensor, is once engine up to your normal temp of 70 is to remove the reservoir caps asap. relieving any pressure slowly & compare actual coolant temperature with gauge using a meat thermometer.
Hoggy.


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## davidf1 (Jun 10, 2013)

Do you mean where you put the coolant in.could I do it by opening the reservoir cap,then starting engine and let it get to the 70 degrees and put thermometer into reservoir,


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## Hoggy (May 8, 2002)

davidf1 said:


> Do you mean where you put the coolant in.could I do it by opening the reservoir cap,then starting engine and let it get to the 70 degrees and put thermometer into reservoir,


Hi, You may be able to but I expect with running engine it will "boil" over & you will loose some coolant & make a mess.
Hoggy.


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## hunaink (Feb 15, 2016)

Sorry to revive a dead conversation. I did a log run last night and have the data here but just trying to figure out what i should be comparing the Coolant Temperature reading with (to find a possible correlation).

Trying to work out If there is anything i can find in the data that might obviously scream THERMOMETER as mine can be quite temperamental.

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## poder (Mar 18, 2015)

You should be able to correlate with engine oil temperature. On my 2006 2.0 TFSI, the coolant temperature is around 20 degrees Celsius higher than the oil temp. When coolant is 60, oil is 40 and when coolant reaches 90, oil is at 70. After that the oil temperature also rises to 90 and they stay pretty much the same afterwards.
So, with a fully warm engine (probably around 10-15 min. driving), you can check both temperatures. If oil says 90 and coolant 70, my guess is that the coolant temp. sensor is faulty. If oil is lower also, e.g. 75, my guess is the thermostat.


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## TT-driver (Sep 14, 2010)

Since there is a heat exchanger between the oil and the coolant, the above makes sense to me


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## hunaink (Feb 15, 2016)

Awesome, i'll crunch the numbers and stick up the graph with insights! Going to be a fun 1st day back at work 

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## poder (Mar 18, 2015)

Just checked again today in the colder weather and it was more like 10-15 degrees difference between oil and coolant. Last I checked it was quite a bit warmer


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## hunaink (Feb 15, 2016)

Turns out you cant take measurement of Oil Temp from the OBD port... looked at the coolant temp however and seems to be hovering between 65 & 69 the full length of 20 min motorway drive. Sounds like i need a new one too me. Any conflicting views?

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## poder (Mar 18, 2015)

Sure you can, this is a graph of the readings I took on my car using VCDS (before changing the thermostat): download/file.php?id=259745


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## efunc (Oct 12, 2008)

HarboroughTT said:


> Does your car get to 90degrees if you are sat in traffic? I had this issue not long back, the car would never quite get to the correct temperature unless in traffic. Mine was the thermostat, got a mobile mechanic to change it out and now it sits bang at 90. Just make sure you have spare coolant when changing the thermostat as he lost around 3 litres when changing it.


Do you mind me asking how much the job cost? I need to book mine in because I'm getting excessive white smoke from the exhaust. I have a suspicion though that it might be the thermostat to blame because it mostly sits at 80-85 and rarely makes it all the way to 90 degrees. I'm going to book a diagnosis with my local indy, but that costs £90 on its own. If following up my hunch and fitting a thermostat is not much more it could save a fair wedge of cash. I just tried to call Audi to price up the job, but couldn't get through. Thanks


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## hunaink (Feb 15, 2016)

My apologies, probably should have been more specific. I don't yet hace VCDS i was just using the dash command app via the OBD which unfortunately doesn't show oil temp. But efunc just solidified my suspicions as mine gives out ALOT of white smoke and i've always put it down to condensation!

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## efunc (Oct 12, 2008)

Blimey, £280 to fit a new thermostat at my local independent! I wasn't expecting that. Anyone pay less for this job?


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## poder (Mar 18, 2015)

Well, it's not an easy job [smiley=bigcry.gif] The part itself is not expensive though, so you can always get you spanners out [smiley=book2.gif]


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## efunc (Oct 12, 2008)

no chance!

I realise it's right down next to the block, but figured it'd be cheaper than that. I think I'll have to live with a dodgy stat :?


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## TT-driver (Sep 14, 2010)

Slowly killing the engine because it's always running cold might not be the right way forward... :wink:


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## efunc (Oct 12, 2008)

TT-driver said:


> Slowly killing the engine because it's always running cold might not be the right way forward... :wink:


I know. They've got the car now for a £90 diagnosis, so I'll see what they find. If it's the thermostat then that'll be a further £280 [smiley=bigcry.gif]


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## TT-driver (Sep 14, 2010)

90 quid diagnosis... 
Pretty expensive for finding a known issue. Thermostats do die at some stage...


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## efunc (Oct 12, 2008)

TT-driver said:


> 90 quid diagnosis...
> Pretty expensive for finding a known issue. Thermostats do die at some stage...


The diagnosis was to investigate white smoke, and there are many lines of investigation to explore really. I just heard back from them and they don't believe there is particularly excessive smoke. If anything they said it might be slightly black, but not excessive. They suggest it could indicate the engine running rich. The only two faults I scanned were:

EVAP Emission Control Sys - P0441 - 002 - Incorrect Flow - Intermittent
and 
Boost Pressure Control Valve (N249) - P2261 - 008 - Mechanical Malfunction - Intermittent

Neither have been a noticeable issue in everyday driving and both are common at my mileage. But nonetheless I'll go ahead and fit a new EVAP and pipe for a further £150. As the mechanic said, spending money is optional; none of it is particularly essential to do, but once you start fitting things by trial and error the costs can run out of hand


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## hunaink (Feb 15, 2016)

Just got a quote for £120 fitting from my respected Indie who is also an official APR reseller. Said the job should be 3 hours or so.

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## TT-driver (Sep 14, 2010)

I see. 
The white smoke could well be steam (Water) from the exhaust. As the engine isn't reaching the operating temperature, the exhaust might stay a bit cold. A cold exhaust collects water. Once it gets a bit warm, a lot of steam appears until the exhaust is dry again.


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## efunc (Oct 12, 2008)

TT-driver said:


> I see.
> The white smoke could well be steam (Water) from the exhaust. As the engine isn't reaching the operating temperature, the exhaust might stay a bit cold. A cold exhaust collects water. Once it gets a bit warm, a lot of steam appears until the exhaust is dry again.


Yes, and it my rear view mirror it maybe looks worse than it is. Sometimes it looks quite alarming when I'm sat at traffic lights. The problem is my commute to work is only about 25mins, and in that time it barely makes it to 80 degrees or so. My car never really gets a good run these days. The garage didn't really think there was much of a problem with it, so who knows. I would definitely fit a new thermostat though if it didn't cost me almost £400!


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## efunc (Oct 12, 2008)

hunaink said:


> Just got a quote for £120 fitting from my respected Indie who is also an official APR reseller. Said the job should be 3 hours or so.


If you don't mind me asking, where are you based?? I can't get my head around that quote. Even if the part only costs about £30 (no idea, just guessing) that means your garage is charging £25 an hour before VAT for labour. How on earth can they pay the bills?

Who cares, I want to book in a full service and a bunch of other jobs


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## Hoggy (May 8, 2002)

Hi efunc, As stated, Running cool is not good for the engine or the wallet long term.
Hoggy.


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## efunc (Oct 12, 2008)

Yes, sure, but I'm also wondering if I'm experiencing normal or abnormal behaviour before jumping in with my wallet. After a 25min drive through town in the winter months should I expect my gauge to get right up to 90 degrees, or is it usual to take longer? I know a few months ago it would get to 90 after about 15 mins, although I can't think outside temp has much to do with it. I may have to do this job myself though if I can't find a cheaper quote.


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## Hoggy (May 8, 2002)

efunc said:


> Yes, sure, but I'm also wondering if I'm experiencing normal or abnormal behaviour before jumping in with my wallet. After a 25min drive through town in the winter months should I expect my gauge to get right up to 90 degrees, or is it usual to take longer? I know a few months ago it would get to 90 after about 15 mins, although I can't think outside temp has much to do with it. I may have to do this job myself though if I can't find a cheaper quote.


Hi, Yes it should show 90 after a few miles even in the winter, should certainly be at 90 long before 25 minutes.
Hoggy.


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## efunc (Oct 12, 2008)

Thanks


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## poder (Mar 18, 2015)

Hoggy said:


> Hi, Yes it should show 90 after a few miles even in the winter, should certainly be at 90 long before 25 minutes.
> Hoggy.


I have never had a car that would go from -10 to +90 degrees celsius on a few miles. Okay, it depends how long it will take you to drive those miles, but mine (with a new thermostat) takes about 10 minutes and probably 5-8 miles to get to 90 in the winter.
I would agree that it should reach that long before 25 minutes though :wink:


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## hunaink (Feb 15, 2016)

efunc said:


> hunaink said:
> 
> 
> > Just got a quote for £120 fitting from my respected Indie who is also an official APR reseller. Said the job should be 3 hours or so.
> ...


Haha maybe its mates rates because i get all my stuff done from him. Also that doesn't include the part. He mentioned it might take 3 hours so thats about £35/£40 per hour? Which i think is the going indie rate isn't it?

Anyways picking the part up from Audi tomorrow, any ideas if it will cone with the right o ring or will i need to source a separate one? I hear reusing the current one can be trouble!

Also i'm based in West London and the place is called Wrench Studio.

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## TT-driver (Sep 14, 2010)

When the car is idling in traffic, it may get warmer as there is no cooling wind. And thus steam starts escaping, from the oil and from the exhaust.

There are 2 sources of steam in a car: 
1) burning fuel results in CO2, water and power. -> good
2) a coolant leak -> not good.

So if the coolant level isn't dropping, the steam is coming from the fuel.


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## efunc (Oct 12, 2008)

hunaink said:


> efunc said:
> 
> 
> > hunaink said:
> ...


Is that run by Bill by any chance? I used to go down to bills beetles on Viveash Close all the time, next to the London Motor Museum. But Wrench isn't an Audi Specialist is it?? My car's at rac-london.co.uk at the moment, one of the best Audi specialists in London, and the rates are pretty high, but fairly average for this level of service. I may give wrench a call and see if they sound OK.


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## Hoggy (May 8, 2002)

poder said:


> Hoggy said:
> 
> 
> > Hi, Yes it should show 90 after a few miles even in the winter, should certainly be at 90 long before 25 minutes.
> ...


Hi, If the heater is on full blast, yes it may take a little longer.
Never gets to -10 in South Pembs 

Hoggy.


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## hunaink (Feb 15, 2016)

efunc said:


> hunaink said:
> 
> 
> > efunc said:
> ...


Check them out on Facebook. Last time i was there they had a Ferrari 430 in for a exhaust change & a new RS6 in for a full stage 2 yesterday, i reckon they'll be fine with my £8k TT haha

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## poder (Mar 18, 2015)

hunaink said:


> Anyways picking the part up from Audi tomorrow, any ideas if it will cone with the right o ring or will i need to source a separate one? I hear reusing the current one can be trouble!


Mine came with a new o-ring.


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## efunc (Oct 12, 2008)

poder said:


> hunaink said:
> 
> 
> > Anyways picking the part up from Audi tomorrow, any ideas if it will cone with the right o ring or will i need to source a separate one? I hear reusing the current one can be trouble!
> ...


Yes. Is the part 06F121111F? I can find them for about £38 on ebay? Is that the same as the dealer?


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## TT-driver (Sep 14, 2010)

Given the amount of work involved in fitting a new one, I wouldn't risk getting the part from ebay. Not all car parts on ebay are 100% original... even when it says OEM in the add.


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## hunaink (Feb 15, 2016)

TT-driver said:


> Given the amount of work involved in fitting a new one, I wouldn't risk getting the part from ebay. Not all car parts on ebay are 100% original... even when it says OEM in the add.


Yup thats right, i just picked up one from West London Audi this morning, cost £38 as well but at least i know its from Audi.

If you want yours done urgent, you're welcome to pick up mine of me as i'm on holiday tomorrow and wont be back for two weeks so not really planning on having it done soon. Was hoping i'd get fit in today but it was wishful thinking!

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## davidf1 (Jun 10, 2013)

Who can supply and fit a new thermostat to my car,as mine is needing replacing


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## efunc (Oct 12, 2008)

hunaink said:


> i just picked up one from West London Audi this morning, cost £38 as well but at least i know its from Audi.
> 
> If you want yours done urgent, you're welcome to pick up mine of me as i'm on holiday tomorrow and wont be back for two weeks


Thanks for the offer, tempting! Unfortunately I'm working flat out for almost 3 weeks now, so it won't get done until february most likely. I'll call your guys in Hayes and see if they can match the deal. If so I'll give it bash. Might see how you get first though, so please keep me posted!


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## poder (Mar 18, 2015)

efunc said:


> Yes. Is the part 06F121111F? I can find them for about £38 on ebay? Is that the same as the dealer?


Yes, that's the part number I got. Don't recall what I paid and also I'm in Denmark... Something like this I wouldn't buy on ebay either, not worth the risk considering the amount of work to replace it.


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