Working temperature on 2.0 TDIe during winter time

[Novica]

Hello,

I need urgent reply as I will do timing belt service on this Friday and if I have to change thermostat that is good moment to do it.

As I have bought my car this summer and it is first winter that I am driving it on low temperatures, I have noticed that if I am driving it downhill with low RPM (arnd 1500rpm) the temp gauge needle going slowly down from 90 to lets say 80-75 (little above middle line which is between 50 and 90). Outside temperature is +5 degrees C and internal (cabin) heating is on and set on 23 degrees C. As soon as I start adding throttle on even road or uphill temperature is going to 90 and never pass above 90. The car is getting fast 90 if cabin heating is off, also is getting 90 even if cabin heating is on when i am going outside the town in this winter time. During summer time the temp gauge nedle was always on 90 and never fluctuate. This is first time that I see that she is moving below 90 on this winter time (mostly on temperatures which are below +10 degrees C).

The car is Audi A6 C6 model, CY 01/2011 year, 2.0 TDIe 100kw, 180000km on clock, sedan.

I am asking if somebody who has same car notice similar behavior or the temp gauge needle is fixed all the time on 90 regardless outside temperature?

Thanks for fast replay, I appreciate it.

Kind regards

Novak

[Guest 2]

correct, what you're seeing is normal for cold temps.

[Novica]

correct, what you're seeing is normal for cold temps.

Many thanks Chris for your fast reply.

As I have driven A4 B6 1.9 tdi 2004, the needle was fix all the time. Even when temperature was going on 80 degrees C or up to 100 (monitored on Vag Com) the needle was showing always 90 regardless outside temperature. But when I get failure of thermostat during summer time (when outside temperature is around 30 degress) the needle was going down on downhill road up to 70 degrees.

The story here is different, but I was a little surprised when I saw small fluctuation of temp gauge needle. If it is happening to you guys as well then I will not change thermostat. Suppose that it is working properly.

[Guest 2]

Happens both on my 2009 A3 and 2015 A4, moreso if you're sucking the heat out of the system with the heater.

[royclark]

90 is your thermostat setting. This is the correct operating temperature for your engine.

[Novica]

Happens both on my 2009 A3 and 2015 A4, moreso if you're sucking the heat out of the system with the heater.

Thanks Chris, that is enough for me. So this is normal behavior and I will not touch thermostat. I suppose that if thermostat is always open engine will never get 90 degrees.

Regards

Novak

[Novica]

Thanks Royclark,

I am happy to hear that

:)

[Novica]

Good morning to All,

Just for information, I have checked time and distance this morning as soon as car get 90 degrees from cold engine.

Outside temperature was +4 degrees, cabin heating switched off. Car was driven inside town with average speed 45 km/h, passed 7,6 km in 10 minutes, driving RPM from 1500 - max 2200(on changing gear), mostly flat road and after that temperature gauge needle hit 90 degrees. Then continuing driving few more 100-300 meters, temp gauge needle was going up and down, approximately 1-2 milimeters below 90 degrees all depending if the car is under loading or coasting without throttle. When I reach destination after 8.4 km and 11 minutes the needle was at 90 degrees and stay on it until I parked the car. All the time cabin heating was off.

[royclark]

Good morning to All,

Just for information, I have checked time and distance this morning as soon as car get 90 degrees from cold engine.

Outside temperature was +4 degrees, cabin heating switched off. Car was driven inside town with average speed 45 km/h, passed 7,6 km in 10 minutes, driving RPM from 1500 - max 2200(on changing gear), mostly flat road and after that temperature gauge needle hit 90 degrees. Then continuing driving few more 100-300 meters, temp gauge needle was going up and down, approximately 1-2 milimeters below 90 degrees all depending if the car is under loading or coasting without throttle. When I reach destination after 8.4 km and 11 minutes the needle was at 90 degrees and stay on it until I parked the car. All the time cabin heating was off.

Looks to be working OK.

[Novica]

Thanks Royclark, I will not replace thermostat. Tomorrow I am doing timeng belt.

[B5NUT]

As your car is 5 years old I would change the thermostat regardless, they are cheap enough and if you are changing the water pump then you have to drain the coolant anyway. Thermostats don't last forever, and next time the belt will be done is in another 5 years making the stat 10 years old, and on the 2.0TDi engine it will most likely have failed by then.

[Novica]

Thanks for you opinion B5NUT, I was also thinking about it.

I am already changing alternator free pulley due to fear of failure until next cam-belt change. I am changing water pump with all coolant as well. I was thinking to change as well thermostat, but I do not have time to order original one and I do not know which aftermarket to buy.

I was thinking to wait until this fail and then to change. I know that I should change as well coolant then.

If I buy some aftermarket part in my place, I am not sure if this will last until next timing belt change.

[B5NUT]

I would not touch aftermarket version, just get a genuine one. As the 2.0TDi engine was used in all the VW range you should be able to get one from a local vw,seat or skoda garage.

[Novica]

I will think about it, maybe is better preventive repair then corrective after. I will see if I can get one during day tomorrow, if not then will remain his original.

Thanks for replay again

Novak

[crazy4alfa]

it does sound like thermostat is failing. Once the car is up to 90 it should stay there unless you leave the car idle for a long period.

[Novica]

So, I have finished timing belt service. I did not change thermostat. But, today, on country roads, at ambient temp of -2 degrees, going downhill, few kilometers, the temp gauge go below 70 even closer to 50 then to 70. Cabin heating was on. Then I switched off heating and temperature gauge go above 70 but did not reach 90, as soon as I go on flat road or uphill, temperature go to 90 and everything is fine.

I was searching on net and there is lots of similar behavior but I found on one thread that Audi has 2 thermostats and one guy had similar problems (gauge fluctuate only on winter time) and on the end it was some EGR thermostat.

Then, I have looked at E... manual and saw that on coolant hoses diagram is really two thermostats, main under No.15 and EGR - "hose thermostat" under No. 10.

http://images.tapatalk-cdn.com/16/01/17/61f6667fe423b15b8fa4f33fa4da8dc1.jpg

If you follow that diagram, and you suppose that EGR thermostat is stuck open, then when car is going down hill, exhaust gases cannot heat enough coolant and that coolant is finishing into engine and not into radiator resulting in faster cooling of engine. As soon as you go on flat road or uphill, you give some throttle and exhaust gases are warmer and in this manner heat engine faster.

I did not check if I really have this thermostat but I will investigate it these days and if I have it, I will try to block return to engine and see if it will help in keeping temperature at 90 degrees during going downhill.

I have notice that on net there is huge problems about this EGR thermostat on BMW cars. But for Audi I could not find except one thread.

Here it is one more diagram:

http://www.partscats.info/audi/en/?i=cat_vag_models&brand=au&number=1288&set=1306&ein=2011&f=648&hauptgr=1234567890&hg=1&grf=012121648&bf=12121&hgug=121&ug=21&parent_id=1756502&detail_id=1756528

As you can see, there is not cat oem number for EGR thermostat only, you have to order whole hose.

Can somebody confirm that this EGR thermostat can cause this gauge fluctuation on downhill (or when engine is not under load) during low ambient temperatures?

[B5NUT]

EGR cooler is pretty small, there is no way it could drop the temperature of the coolant by that much. You should not see temperature drops of that much, once the engine is up to temp then it should hover around the 90deg mark, with around a +/- 10% fluctuation, which you won't see on the dash but can see if your logging with VCDS.

[Novica]

I have ordered yesterday this small thermostat (1K0 121 113 A). As soon as it come I will change it and check if there is any improvement. I am hoping that this small thermostat is causing these drops of needle on low ambient temperatures. I read on net (in skoda forum) that they had similar issues as I have, only difference that they have DSG transmission.

[Novica]

Hello,

Update, today I have received this small thermostat. I have noticed that when I blow air through it, the air passes a lit of bit, not so much.
http://images.tapatalk-cdn.com/16/01/30/d7644c978bea05962d9c2ba07c99d902.jpg
This evening I have replaced. The old thermostat does also pass small quantoties of air when I blow it through.
I have tried car and no improvments. The outside temperature was aroung 9 degrees C, cabin heating was on 23 degrees C (AC on and fan was working all the time). Car get working temperature in 10 minutes and in 15 km. On flat road and uphill temperature gauge is on 90. But, when I am going downhill, without any load on engine, after few minutes the temperature gauge is moving from 90 to 80, as soon as I put some load it returns again to 90. The car was driven 50 minutes.

Remained only to change this main (big) thermostat.

Will check more these days the behaviour of temperature gauge and if there are big fluctuations (that gauge is going below 70) I will order main thermostat.

Will keep you advised.

Cheers

Novak

[rowdy-999]

Have you considered the temperature sender or gauge may be faulty, or as suggested its a normal trait?
I can't see how even a faulty thermostat, once up to normal temperature could suddenly cause a drop in working temperature? The thermostat is already fully open, so it cant open any more, causing extra cooling.

I think you're worrying over nothing.
Personally I don't care what my needle says as long as i get heat from the heater, or it doesn't overheat.

[Novica]

I suppose that gauge is OK as this happen only when heating is on, ambient temp is below 10 degrees C and engine does not have any load (going downhill). Heating in cabin is OK all the way (anyhow, car has auxiliary heating. So when there is no heating from engine it switch on this auxiliary heating).
I will monitor it these days, but, I had A4 with 1.9 tdi PD, and gauge was steady on 90 all the time, can go down but only when outside is 15-20 below 0.
I dont like if something is wrong to take it as it is. I am new to the car, this is may first winter with it, maybe is normal like that, but will see these days (will try to contact somebody who has same car and engine).
I only regret that I did not change that thermostat when I was doing timing belt. Good or bad it does not mettar. But next time will be different. This should be considered as consumable part.

[rowdy-999]

I don't believe the thermostat should be considered a consumable part.
5 years is nothing for a 'stat. I've driven 20+ year old cars on the original. I would say they outlast the coolant rad on most cars.

[Novica]

On my previous A4, thermostat failed on 180000 km and 7 years old car. It failed on summer time and I got similar issue, going downhill on ambient temperature of 30 degrees the gauge falling down (with A/C on). So, I am now on same km but car has 5 years, the coolant and everything other were original until timing belt change and now I have new original coolant G13, new original pump and new original small thermostat. I am thinking to change as well new original thermostat.

[necstandards]

Novica - did you come to any conclusion on this?

[Novica]

Novica - did you come to any conclusion on this?
Yes, the engine is working like this. Good friend of mine had A4 (B8) with same engine and less mileage, he changed thermostat (both) and same thing happens. I will change thermostat on next timing belt change. I noticed that if the car is driven on highway on low temperatures the engine is maintaining its working temperature, I suppose that engine will not even reach working temperature if something is wrong. These are high efficient engines.

Sent from my LG-D802 using Tapatalk

[rowdy-999]

Have you actually performed any live data on the coolant temp? I wouldn't trust a dashboard gauge.....usually they read 'low', 'normal' or 'head gasket has gone'.

[dan2485]

Have you had the system vacuum bled to rule trapped air?

[Novica]

dan2485 I have not performed any vacuum bled. I suppose that if there were any air trapped will be untrapped after passed 32000km and 2 years. So far car is getting fast working temp, on highway is not losing temp at all, only happen when there is no load on engine and out temp is les then 10 deg C.

Sent from my LG-D802 using Tapatalk

[dcheng]

Hi, I know this is an old thread, but I am having the same problem with my A6 C7's CGLC engine. I recently changed the main thermostat but problem did not go away. Now I am thinking about changing the second thermostat (the one for EGR cooler), but before I do that I wonder if it's worth replacing the coolant temperature sender (G62).

I logged temperatures of G62 and G83 using VCDS, temperatures for both sensors increased together. So I thought the main t-stat was stuck open causing cold coolant to go into the engine. Upon inspection of old t-stat, it did not look stuck open, and the replacement did not solve the problem. Meaning main t-stat probably wasn't the cause of problem. Could the second t-stat be stuck open causing cold fluid to go into the engine? What do you guys think? Has any one changed both t-stats and solved the problem?

Thanks.

[HydrocarbonPrim]

Hi, I know this is an old thread, but I am having the same problem with my A6 C7's CGLC engine. I recently changed the main thermostat but problem did not go away. Now I am thinking about changing the second thermostat (the one for EGR cooler), but before I do that I wonder if it's worth replacing the coolant temperature sender (G62).

I logged temperatures of G62 and G83 using VCDS, temperatures for both sensors increased together. So I thought the main t-stat was stuck open causing cold coolant to go into the engine. Upon inspection of old t-stat, it did not look stuck open, and the replacement did not solve the problem. Meaning main t-stat probably wasn't the cause of problem. Could the second t-stat be stuck open causing cold fluid to go into the engine? What do you guys think? Has any one changed both t-stats and solved the problem?

Thanks.

I have same problem, I have replaced egr thermostat, main thermostat and non return valve, no difference so far.

I don't think its normal, if coolant isn't up to temp the DPF won't regen.

[dan2485]

Google SSP 608

this explains the coolant circuit modes which may help you diagnose the issue.

[dcheng]

I have same problem, I have replaced egr thermostat, main thermostat and non return valve, no difference so far.

I don't think its normal, if coolant isn't up to temp the DPF won't regen.

After changing my main thermostat, the reason I did not continue on with changing the EGR thermostat is that I have seen many on this and other forum who changed both thermostats only to find no difference. Maybe the radiator outlet coolant temperature sender is defective? I wonder if anyone has changed the coolant temperature sender.

[HydrocarbonPrim]

After changing my main thermostat, the reason I did not continue on with changing the EGR thermostat is that I have seen many on this and other forum who changed both thermostats only to find no difference. Maybe the radiator outlet coolant temperature sender is defective? I wonder if anyone has changed the coolant temperature sender.


I'll go through it this Sunday hopefully, I'm not using the car at the moment. I've got use of a thermal imaging camera at work. I will try and bleed it extensively first and then look at auxillery coolant pump and mixing valves and coolant temps on the sensors. I'll report back.

[HydrocarbonPrim]

I've looked through my coolant system today, I checked the orientation of the egr thermostat and non-return valve and they look correct. I also removed and tested the EGR / Auxiliary electric water pump in a bucket of water and that works fine. I then noticed that the egr cooler did not get very warm to the touch after 20mins idling, so removed and cleaned the exhaust gas passages on that, all were blocked except the 2 bigger passages (messy job).

After re-installing it seems little change after 20 mins idling, possibly slightly warmer to touch, however the car does seem to reach 90 quicker (4miles of driving around 2,000rpm at 8.5 degrees C outside air temp).

However the engine temp still drops from 90 after 5 mins idling with cabin heater on max temp and max blow, maybe this is normal?

when I felt the pipes around back of engine after just 20mins idling (not upto full temp) it seems the inline thermostat is doing its job and is closed, it also seems like there is slightly more pressure on the egr cooler inlet than the outlet, I suppose that is to be expected.

I don't expect anymore sub zero days this year so might not know if this is fixed, I suspect the temp dropping at idle (after a run) points to it not being resolved. :-(

If during a -0 day the vehicle heats up after a reasonable drive and the cabin is warm then I suppose the issue is coolant temp sensor / software and I would be happy to leave it at that.

[HydrocarbonPrim]

Google SSP 608

this explains the coolant circuit modes which may help you diagnose the issue.

Thanks Dan but I think that's for the model newer than mine, I read it anyway that coolant system is much more complicated, I'm glad I've got the older C6.

[dcheng]

Here is an update on my car's situation. I changed the coolant temperature sensor (VW part number 06A919501A), put in a new O-ring, and changed coolant, but unfortunately it did not make a difference. Engine temp would still decrease when car is not under heavy load. Seeing so many people's experience on changing main thermostat and EGR thermostat without much success, I think the coolant temperature sender will be the last thing I change, and I will just live with it.

[swalker]

it must be a thing as i got both stats change don my cjca engine as the gauge didn't pass 70. after the first change it was as described above, so i pushed back to the garage and they changed both again for genuine parts - no difference, the garage said good luck, so i went about changing the temp sender, no difference. The sender only had 2 connections, my last 1.9tdi (afn) had 3, a lesser accurate one for the dash. Dont forget the glow plugs now kick in to get the right temp for a re-gen.

[mickeybo]

Why did none of yous mention the very most likely cause of the problem is wiring. thermostats are very easely checked out either on or off the car

[swalker]

the fault is not presenting as electrical.The gauge follows the behavior of engine load, that suggests its ok. I pulled live data and you could see the coolant temperature go up and down in line with my drive home as i did a bit of stop start, motorway driving, sitting in traffic, etc.
if it was electrical i would expect it to be max or min all the time or a constant off set at a push. But we get 90 when we expect it - it just drops in sub 10 weather when the engine is getting it easy.

[dcheng]

I have an interesting discovery that I would like to share with you all.

About a week ago, I cleaned the coolant temperature sensor's connector using WD40's Electrical Contact Cleaner. The coolant temp gauge on my instrument cluster would hit 4 dashes (4th one being 80~90 deg Celsius) on my daily commute, similar to how the car would behave years ago. I then proceeded to using VCDS to log the actual temperature, and I saw a difference between before and after cleaning. Before cleaning the connector, I would usually get about 73 degrees Celsius when I arrive work, but now I would get about 84 degrees Celsius when I arrive work. Even though I did not clean the connectors for engine oil temp and radiator temp sensor, those two would also see a rise in temp when I logged it with VCDS. Although it did not hit 90 degrees Celsius, and temperature would fluctuate (temp dropping when car is going down hill or not under heavy load), it is still nice to see some improvements.

So for those who had changed the main thermostat, EGR thermostat, coolant temp sensor, or only one of the above, or any combination of the three but did not see any difference, I would suggest giving the coolant temp sensor connector cleaning a try. In my case, it made a difference.

[Novica]

Hi All,

I have not be active for long period.

I have even forgot if I have heating problem before or after timing belt change and now I see that heating problem started before timing belt change on winter of 2015 (same year that I bought car on summer time) thanks to this thread :)

I am driving same car, now the clock is on 292000 km.

In meantime, after timing belt change, hose (EGR) small thermostat has been changed and I have changed the main thermostat as well on 2018 (212000 km).

No change, during winter time (as soon as outside temp is below 10) and heating of the cabin is on, engine temperature is going down if there is no load on engine. As soon as Spring arrives everything is normal until next winter time. I accepted this as normal behavior of 2.0 tdi CR engines.

But, each winter I start to doubt ....

Monitoring live data from vcds of the engine coolant temperature and radiator outlet temperature, I have noticed that coolant in radiator is also warming up, slowly, but is going up, especially once coolant of the engine pass 60 degrees coolant in radiator starts to grow up faster (especially if the car is not moving, i.e. on idle).

My guess is that there is mixing of the water between small - engine circuit and bigger - radiator circuit. I suspect that main thermostat is opening before its defined temperature (87 degrees). Few days ago I have tested my old, original, thermostat by heating the water and pouring into thermostat housing, it started to open at abt 70 degrees which is far away from declared 87 degrees. This is confirming my theory that coolant from engine start to mix with coolant from radiator before it is time i.e. thermostat opens before 87 degrees. One more thing that I have noticed is that old testing thermostat is closing slowly passing water which is already 60 degrees warm.

I am sorry that I did not checked the new one and original one back in the time when I have changed them.

My advise is to check new thermostat and old one when you are in process of change it. There is plenty complaints on brand new aftermarket thermostat that they are opening before stated temperature, I suppose that even OEM one can be defected.

My next timing belt is due next year (at 300000km, it is still same OEM timing belt from 2016 when I have changed at 180000 km) and I am going to change the thermostat. As the car is getting older and I do not have intention to by original spare parts anymore, my intention is to buy aftermarket spare parts for timing belt and thermostat, but, next time, first I will test new thermostat and I will test the old one as well. If the new one is opening before declared (87) temperature it will be returned back immediately for next one until I get one that is opening at approximately 87 degrees.

I wish you a good luck in resolving the heating problem on 2.0 TDI CR engines.