Audi B8 2.0 tdi CAGA coolant temp problems

Don Mundo · Jan 20, 2018

Hey.
I'm having some major problem with my car,bought it second hand, came winter and as soon as ambient temperature dropped below +5°c I noticed that my cars engine doesn't want to heat up properly. Needless to say that it happened also after an Audi recall remapping.
At first thought that it's thermostat,obviously,changed it - didn't solve the problem. After that I changed the temperature sensor (Coolant temperature sender), also no change. The temperature doesn't go above 65°c and on a constant speed of 110 km/h drops to around 50.
10'000 km ago changed the water pump (set with drive belt'n'stuff)
Anyone of you maybe had a similar problem and knows the solution for it?

Darren92 · Jan 20, 2018

Diesels especially in winter will always run colder.

Don Mundo · Jan 20, 2018

what about the carbon build-up? or it won't increase due to running on lower temperatures?

KrisKrk · Jan 20, 2018

Did it happen during summer time?

My 2.0 2010 tdi is fine it colder times. Pick up temperature ok. As soon as I switch the heating on and coolant temp is not solid 90 for few miles, it starts to drop.
Also drops when I stop on traffic light and so on.
It pick up again, when back to driving with speed 25-30, as it normally would.

Had thermostat changed February last year and haven’t noticed any difference either.

Think I’m having only winter diesel problem.

Yours sounds more serious.

Can your engine get any temperature at all?

Had problem with my A4 few years back.
Driving on a motorway 60-70 mph and temperature was dropping, coolant was leaking and splashing around the engine.
Turned out it was blown head gasket.

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Don Mundo · Jan 20, 2018

Thank you for your time.
During summer time didn't notice any kind of problems with temperature, maybe I just was unaware, but it's less likely.
Yes,the gasket would have been my next guess,but didn't want to waste any more money just by guessing. The thing is,I haven't noticed any coolant loss, if it's level is dropping then not by much.
While its idle, it goes up to 70+C, but on a highway it drops down to around 55-65C, depends how much I'm pushing the car.

Retroman · Jan 20, 2018

Mine struggles to get to the 12-o-clock 90C position when the ambient temp falls much below 10C. On the longer motorway journey it gets there OK.

Many years ago car owners used to stick a bit of cardboard in front of their radiators in the winter - perhaps Audi should introduce some complex bit of laptop-controlled wizardry to lower a bit of cardboard in front of the radiator in the winter for their diesels. :haha:

KrisKrk · Jan 20, 2018

My A4 was severe under blown gasket issue and coolant was leaking all over. Had to fill up the tank back to levels every tank of fuel or quicker if pushed with faster driving.

It looks like there is a problem with your cooling system.
It does not allow your engine to gain heat and it keep the cooling flow open.

Have you tried cooling system flush?

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Retroman · Jan 20, 2018

Coolant loss causing the engine to run cold??
An engine running too cold can really only be a thermostat issue (if there is an issue). There seems to be a slight range of "opening temperatures" with aftermarket stats so it might be an idea to check exactly what your engine needs and exactly what has been fitted. With regard to carbon being burnt off in the DPF, that is controlled by exhaust temperature (350-500C for passive regens) rather than coolant temperature around 90C.

KrisKrk · Jan 20, 2018

Retroman said:
Mine struggles to get to the 12-o-clock 90C position when the ambient temp falls much below 10C. On the longer motorway journey it gets there OK.

Many years ago car owners used to stick a bit of cardboard in front of their radiators in the winter - perhaps Audi should introduce some complex bit of laptop-controlled wizardry to lower a bit of cardboard in front of the radiator in the winter for their diesels.

Yeah.
Always wondered, why black cabs around drive with cardboard on the grill.

Might drop something behind my grille

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KrisKrk · Jan 20, 2018

Retroman said:
Coolant loss causing the engine to run cold??
An engine running too cold can really only be a thermostat issue (if there is an issue). There seems to be a slight range of "opening temperatures" with aftermarket stats so it might be an idea to check exactly what your engine needs and exactly what has been fitted. With regard to carbon being burnt off in the DPF, that is controlled by exhaust temperature (350-500C for passive regens) rather than coolant temperature around 90C.

With coolant loss, temperature was going up and drop again, in waves.
There was no constant temperature maintained.

You’re right about aftermarket stats.
Guy who replaced mine, tried 5 or 6 of different ones before got the correct one.

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Don Mundo · Mar 3, 2018

So finally I got it fixed and found out what's the problem of my car. The problem was with (Part number) 03L 122 157 M, marked in picture as Nr. 23.

Sadly dealer didn`t tell me important thing, that I got 3+ Thermostats, on the phone they said I got only 1. And after troubleshooting - that I can get the pressure check valve and thermostat of 03L 122 157 M separated from original maker,not from Audi,without buying all the hoses and stuff. So it cost me 180€ instead of 20€ for each of these units,or even less. Anyhow its fixed now and finally I can see 90°C in my dash.

Maybe someone will find this information useful in the future. Take care guys and thanks for the suggestions.

mladen · Apr 19, 2018

Don Mundo said:
So finally I got it fixed and found out what's the problem of my car. The problem was with (Part number) 03L 122 157 M, marked in picture as Nr. 23. View attachment 149959
Sadly dealer didn`t tell me important thing, that I got 3+ Thermostats, on the phone they said I got only 1. And after troubleshooting - that I can get the pressure check valve and thermostat of 03L 122 157 M separated from original maker,not from Audi,without buying all the hoses and stuff. So it cost me 180€ instead of 20€ for each of these units,or even less. Anyhow its fixed now and finally I can see 90°C in my dash.

Maybe someone will find this information useful in the future. Take care guys and thanks for the suggestions.

Hi Don, my assumption is the inline stat only exists on automatic transmissions? Otherwise there is only the main stat on manuals?

Don Mundo · Apr 20, 2018

mladen said:
Hi Don, my assumption is the inline stat only exists on automatic transmissions? Otherwise there is only the main stat on manuals?

Can't tell you about other cars,not working in a field. I know only about mine, the 2.0tdi CAGA with 8-speed CVT.

csaba95 · Feb 1, 2020

Don Mundo said:
So finally I got it fixed and found out what's the problem of my car. The problem was with (Part number) 03L 122 157 M, marked in picture as Nr. 23. View attachment 149959
Sadly dealer didn`t tell me important thing, that I got 3+ Thermostats, on the phone they said I got only 1. And after troubleshooting - that I can get the pressure check valve and thermostat of 03L 122 157 M separated from original maker,not from Audi,without buying all the hoses and stuff. So it cost me 180€ instead of 20€ for each of these units,or even less. Anyhow its fixed now and finally I can see 90°C in my dash.

Maybe someone will find this information useful in the future. Take care guys and thanks for the suggestions.

Dear Don Mundo!

I have the same problem (2008 Audi A4 tdi CAGA, 8 speeds CVT), but I don't understand everything. (My English is bad!) What solved your problem? Was that hose which number 's 03L 122 157 M? Are you sure that to a simple hose solve this complex problem or it's not a simple hose? Would you write again your full story for me/us, please! Your story became impenetrable at the end of the forum page.
Sorry for the many question!

Thank you in advance for your help!

Csaba

DarthVAG · Oct 12, 2020

Don Mundo said:
So finally I got it fixed and found out what's the problem of my car. The problem was with (Part number) 03L 122 157 M, marked in picture as Nr. 23. View attachment 149959
Sadly dealer didn`t tell me important thing, that I got 3+ Thermostats, on the phone they said I got only 1. And after troubleshooting - that I can get the pressure check valve and thermostat of 03L 122 157 M separated from original maker,not from Audi,without buying all the hoses and stuff. So it cost me 180€ instead of 20€ for each of these units,or even less. Anyhow its fixed now and finally I can see 90°C in my dash.

Maybe someone will find this information useful in the future. Take care guys and thanks for the suggestions.

Hi Don Mundo, I have the A4 B8 2.0Tdi CAGA manual A4. I've only had it for a couple of weeks, but have noticed that the temperature is is very erratic.

With an outside ambient of say 12 -18 degrees - Motorway driving at 70-80mph the motor temp drops to around 60 degrees, when I'm in traffic it levels off at the normal 90 degrees and stays there until you get some speed going again.

I don't have a coolant leak, as I haven't had to top this up in any way. I haven't tried changing the thermostat yet, as I've read that others have tried this without any success.

If I read your post correctly, you had your issue put down to a hose (Part no 23 in that diagram?).

I have read elsewhere there are several thermostats in the A4... not just the standard round one that everyone is replacing without much success.
There is also a 'VERNET THERMOSTAT' - I will include a picture of this. From your diagram it looks like it may be part no 37? but I can't be sure.
DId the guy you speak to elaborate on any information on the location/nature of the other thermostats at any point?

Another question, where did you get that schematic from? It's very helpful.

KRUTO · Dec 28, 2020

Don Mundo said:
So finally I got it fixed and found out what's the problem of my car. The problem was with (Part number) 03L 122 157 M, marked in picture as Nr. 23. View attachment 149959
Sadly dealer didn`t tell me important thing, that I got 3+ Thermostats, on the phone they said I got only 1. And after troubleshooting - that I can get the pressure check valve and thermostat of 03L 122 157 M separated from original maker,not from Audi,without buying all the hoses and stuff. So it cost me 180€ instead of 20€ for each of these units,or even less. Anyhow its fixed now and finally I can see 90°C in my dash.

Maybe someone will find this information useful in the future. Take care guys and thanks for the suggestions.

Thank You very much. I got this problem on my Audi A4 B8 2.0 TDI 105 kW CAGA, 8 CVT. Before I found this topic, I changed water pump, engine termostat, nothing changed. Then I change only termostat on that hose, nothing changed. When I change all that hose (in image - part number 23), problem is solved! Thanks man!

Nobody in Bratislava (Slovak Republic) can solved this problem. In Audi service they said - this is normal with that engine

Then I found Your topic. You saved me, You saved my car

Many thanks again!

DarthVAG · Dec 28, 2020

for me it was the vernet thermostat as illustrated above. i;'ve been reading that 'it's normal for the car not to reach the 90 degrees' in quite a few places, but didn't believe this (i also have a A6 which heats up to 90 wihtin 5 minutes)... if the car doesn't run at 90, you will have problems with fuel efficiency, winter cabin heat and probably in the long run DPF issues.
anyway - I chanegd the vernet thermo, it was a complete b!!ch to get out and in (lots of awks bolts), but within 5 minutes of test drive after installation... BIIIINGO... winner winner chicken dinner.... the car reached and stayed at 90 degrees. thank god that's sorted. next to do an emergency DPF regen to clean that out...

DarthVAG · Dec 28, 2020

oh and the schematics... are here:

http://www.oemepc.com/audi/

bobby singh · Jan 20, 2021

I haven't read all this read but 3.0TDI's get the same problem and its normally the EGR stat

zergling86 · Jan 20, 2021

Audi A4 B8 2.0 caha caga... All 2.0 diesel engine have two termostat and cooling valve.
1st Engine main termostat.
2nd termostat pipe termostat

factory number:1K0121113A
Valve factory number:1J0122351

Yes the two car parts have in the diagram (23 pipe number).

Facelift same but the valve of into a pipe. And another oem number.

Look at the pictures the google.
Write the oem number
1K0121113A
1J0122351

Do it!.

Best regards
Tamas (from Hungary)

Mirec · Feb 6, 2021

Hi Kruto. You are my hope in here. I am not sure if can text you here in slovak language.
Can you please give me your FB or something I need ask you about that hose. I have the same problem with my A4 B8 2.0tdi
Dik

nomad90 · May 7, 2021

Don Mundo said:
So finally I got it fixed and found out what's the problem of my car. The problem was with (Part number) 03L 122 157 M, marked in picture as Nr. 23. View attachment 149959
Sadly dealer didn`t tell me important thing, that I got 3+ Thermostats, on the phone they said I got only 1. And after troubleshooting - that I can get the pressure check valve and thermostat of 03L 122 157 M separated from original maker,not from Audi,without buying all the hoses and stuff. So it cost me 180€ instead of 20€ for each of these units,or even less. Anyhow its fixed now and finally I can see 90°C in my dash.

Maybe someone will find this information useful in the future. Take care guys and thanks for the suggestions.

where did you get this diagram from?

zergling86 · May 11, 2021

Hy!
Yes, number is 23! It have two parts! And I must be change main thermostat. (CAHA,CAHB, CAGA,CAGB,CAGC)
1K0121113A
1J0122351
All problems are solved!

However for the facelift model the temperature drop does not always resolve there. (CJCA,CJCB,CJCD,CGLC etc.
Part number is another. I attached the picture! The valve is hidden in the pipe.
1K0121113A
3W0122351 (Facelift model) 2012-......
There is always something fault with this.
There is a 50% chance of it.

Best regards,
Tamás!

nviktor01 · May 21, 2021

zergling86 said:
Hy!
Yes, number is 23! It have two parts! And I must be change main thermostat. (CAHA,CAHB, CAGA,CAGB,CAGC)
1K0121113A
1J0122351
All problems are solved!

However for the facelift model the temperature drop does not always resolve there. (CJCA,CJCB,CJCD,CGLC etc.
Part number is another. I attached the picture! The valve is hidden in the pipe.
1K0121113A
3W0122351 (Facelift model) 2012-......
There is always something fault with this.
There is a 50% chance of it.

Best regards,
Tamás!

Hi Tamás!

Do you know if this problem affects poor diesel consumption issues?
I think my A4 B8 2.0 tdi CGLC is eating too much. ~8,5L/100km at 140km/h and around 10-13 in the city.

Thanks for your answer,
Viktor
Hungary

Rabee · Dec 22, 2021

zergling86 said:
Hy!
Yes, number is 23! It have two parts! And I must be change main thermostat. (CAHA,CAHB, CAGA,CAGB,CAGC)
1K0121113A
1J0122351
All problems are solved!

However for the facelift model the temperature drop does not always resolve there. (CJCA,CJCB,CJCD,CGLC etc.
Part number is another. I attached the picture! The valve is hidden in the pipe.
1K0121113A
3W0122351 (Facelift model) 2012-......
There is always something fault with this.
There is a 50% chance of it.

Best regards,
Tamás!

skyisblue · Jan 19, 2022

Hi,

I am having same issue with temperature as well it reaches 90 on gauge while on motorway but drops once you get off motorway heating works fine when facing up (windscreen) & vents but not in foot well.

Replaced few parts but still same issue its drinking diesel like mad (only does 400 miles out of full tank) independent Audi specialist who did repairs he gave up as well now is there anything else to look for and i desperately need the car for work due to high mileage every day.

(Audi a4 2013 tdi 2.0 cvt) not sure exactly what engine i have like caha or caga ...

Parts Replaced :

Full cam belt kit done including water pump plus full service at same time

Main thermostat replaced as far as i know he replaced it with genuine part

secondary inline thermostat

electric regulator valve

please put me in some direction so i can get someone to sort it out for me or if you recommend anyone around Manchester.

thank you in advance !

Svizoman · Jan 20, 2022

Don Mundo said:
Hey.
I'm having some major problem with my car,bought it second hand, came winter and as soon as ambient temperature dropped below +5°c I noticed that my cars engine doesn't want to heat up properly. Needless to say that it happened also after an Audi recall remapping.
At first thought that it's thermostat,obviously,changed it - didn't solve the problem. After that I changed the temperature sensor (Coolant temperature sender), also no change. The temperature doesn't go above 65°c and on a constant speed of 110 km/h drops to around 50.
10'000 km ago changed the water pump (set with drive belt'n'stuff)
Anyone of you maybe had a similar problem and knows the solution for it?

that is thermostat 100%. i dont know what you have changed but i guess you did not make it ok. take it to a profesional to change engine thermostat. it is 4/2 way plastic housing

Svizoman · Jan 20, 2022

skyisblue said:
Hi,

I am having same issue with temperature as well it reaches 90 on gauge while on motorway but drops once you get off motorway heating works fine when facing up (windscreen) & vents but not in foot well.

Replaced few parts but still same issue its drinking diesel like mad (only does 400 miles out of full tank) independent Audi specialist who did repairs he gave up as well now is there anything else to look for and i desperately need the car for work due to high mileage every day.

(Audi a4 2013 tdi 2.0 cvt) not sure exactly what engine i have like caha or caga ...

Parts Replaced :

Full cam belt kit done including water pump plus full service at same time

Main thermostat replaced as far as i know he replaced it with genuine part

secondary inline thermostat

electric regulator valve

please put me in some direction so i can get someone to sort it out for me or if you recommend anyone around Manchester.

thank you in advance !

this engine doesnt have 2nd thermostat and no regulator valves. there is only engine thermostat. regulator valve is only used for cabin heater.

skyisblue · Jan 25, 2022

Svizoman said:
this engine doesnt have 2nd thermostat and no regulator valves. there is only engine thermostat. regulator valve is only used for cabin heater.

Hi,
I have just checked my logbook as i have no idea what engine version i have and its 2013,B8, LCJCDF1, CJCD****does this version only have one thermostat if so even after replacing all the related parts whats causing the issue do you think ….he said they have replaced main thermostat with genuine part , inline/regulator valve and check regulator valve with genuine parts again..... and it still drops temperature on gauge.

I have attached an image after driving for 40 minutes most part was motorway soon got off the motorway it dropped to what it shows in picture and not giving me best mpg as well, if you recommend shall i ask him to replace thermostat again, by the way heating works fine as far as i know but does drops coolant temperature.

Thanks alot for your input really in need of some useful information.

Daveabuk · Feb 12, 2022

Having the same problem here. 2014, CAGA manual. 117k.

Driving to work is 11 miles of 60mph B roads with about 15 roundabouts. Takes around 20 mins. Constant driving, no stopping, coasting and pulling away. Temp gets to about 75c on the gauge and oil gets to around 80c on the lap timer. Heaters on number 4 set at 22c on Auto mode. The heaters get quite warm (not hot) after doing about 2 miles. Half way to work they are hot.

If I put my foot down, I do get 90c. But when lifting off it drops back to 75c(ish). If I turn heaters off, I get 90c and it stays there.

Timing belt and water pump changed by Audi on 95k. EGR & cooler replaced on 105k and added coolant mix of 50/50. Coolant is at max and has never moved since replacement.

Today I have just replaced 1K0 121 113 A. The inline thermostat/one way valve. Genuine VAG part.

Been for a test drive, temp stays the same about 75c but gets there a lot faster.

I changed this part as many people said it's normally the one that has cured their heat problems.

What would the next course of action be? Coolant temp sensor or main thermostat?

Thanks.

skyisblue · Feb 12, 2022

Daveabuk said:
Having the same problem here. 2014, CAGA manual. 117k.

Driving to work is 11 miles of 60mph B roads with about 15 roundabouts. Takes around 20 mins. Constant driving, no stopping, coasting and pulling away. Temp gets to about 75c on the gauge and oil gets to around 80c on the lap timer. Heaters on number 4 set at 22c on Auto mode. The heaters get quite warm (not hot) after doing about 2 miles. Half way to work they are hot.

If I put my foot down, I do get 90c. But when lifting off it drops back to 75c(ish). If I turn heaters off, I get 90c and it stays there.

Timing belt and water pump changed by Audi on 95k. EGR & cooler replaced on 105k and added coolant mix of 50/50. Coolant is at max and has never moved since replacement.

Today I have just replaced 1K0 121 113 A. The inline thermostat/one way valve. Genuine VAG part.

Been for a test drive, temp stays the same about 75c but gets there a lot faster.

I changed this part as many people said it's normally the one that has cured their heat problems.

What would the next course of action be? Coolant temp sensor or main thermostat?

Thanks.

I am not a mechanic would try main thermostat , mine reaches 90c no issue but drops after less strain on engine or soon you get off motorway it drops down to 75c trust me it’s annoying

Water pump, inline regulator, inline pump, main thermostat everything replaced still the same

John10 · Mar 6, 2022

zergling86 said:
Hy!
Yes, number is 23! It have two parts! And I must be change main thermostat. (CAHA,CAHB, CAGA,CAGB,CAGC)
1K0121113A
1J0122351
All problems are solved!

However for the facelift model the temperature drop does not always resolve there. (CJCA,CJCB,CJCD,CGLC etc.
Part number is another. I attached the picture! The valve is hidden in the pipe.
1K0121113A
3W0122351 (Facelift model) 2012-......
There is always something fault with this.
There is a 50% chance of it.

Best regards,
Tamás!

Hi Tamás
I have a 2011 facelift 2.0 TDI Audi A6 B7 with CGLC engine CVT gearbox
I have changed both (marked with red on photo) the main thermostat (03L121111AD) number 56 and the inline thermostat (1K0121113A) that has no number as it comes with the pipe number 32 (03L122157Q).
Coolant is still not warming fast only under heavy load or acceleration and even then if temperature is low outside it not staying at 90 degrees for to long after.
I have checked to see where is 3W0122351 on my car and from what I have noticed it is in the pipe marked with blue color again with no number attach to it as it looks to be part of the main pipe number 32 (03L122157Q).
Can you please confirm if is there? And is the 3W0122351 correct number for it? I am only asking this because I did not order the complete pipe number 32 (03L122157Q) to replace I buy the parts separate so the only thing that I am missing seems to be this non-return valve 3W0122351.
Thanks

Daveabuk · Mar 8, 2022

John10 said:
Hi Tamás
I have a 2011 facelift 2.0 TDI Audi A6 B7 with CGLC engine CVT gearbox
I have changed both (marked with red on photo) the main thermostat (03L121111AD) number 56 and the inline thermostat (1K0121113A) that has no number as it comes with the pipe number 32 (03L122157Q).
Coolant is still not warming fast only under heavy load or acceleration and even then if temperature is low outside it not staying at 90 degrees for to long after.
I have checked to see where is 3W0122351 on my car and from what I have noticed it is in the pipe marked with blue color again with no number attach to it as it looks to be part of the main pipe number 32 (03L122157Q).
Can you please confirm if is there? And is the 3W0122351 correct number for it? I am only asking this because I did not order the complete pipe number 32 (03L122157Q) to replace I buy the parts separate so the only thing that I am missing seems to be this non-return valve 3W0122351.
Thanks

Hi John,

If you have this hose/valve, look at the top of your engine, above where the inline thermostat is and you should be able to see the one way valve hose. It's a small hose, about 6-8inch long and has a bulge at one end. It is also marked up with green writing and the product code 03L 122 157.
This is the hose that contains the one way valve 3W0 122 351.

I have the same problem as you. Both main thermostat and inline valve replaced. No change. Here are my symptoms:

Outside temp - under 10c
Warm air inside the cabin immediately.
Heater on and the gauge will not go above 75c.
Same with engine oil temperature.
Will go to 90c if doing DPF regen.
Will go to 90c if heaters are off.
Changed thermostat and inline with genuine parts from VW.
Timing belt and water pump changed by Audi 2 years ago (30k miles ago)
I have tried blocking the radiator but it made no difference.
Used VCDS to check the actual readings of the water by reading the sensor and rad output sensor. Both very low and match to gauge on DIS.

Something is taking the heat away from the system and I'm not convinced for one little bit it's the heater matrix. I've owned this car for 5 years and this is the first year it's never gotten to temp.

Hope this helps.

Vladimir777 · Mar 9, 2022

Hi,
I have the same problem, when the outside temperature is below 10 degrees Celsius, the car can't reach 90 degrees, when I drive on the highway it keeps the temperature, but as soon as the car gets off the highway it drops. When the air conditioning fan is turned off, it quickly raises the temperature in the place, as soon as the temperature turns on, it stays in the same place all the time. I changed both thermostats and non-return valve, great service was done at 180k, now the car has 205k. But the problem is there, when the days are warmer I don't notice a drop in temperature. I'm thinking of replacing the water pump again?
And that the car I have is an audi a4 2013. 100kw 2.0tdi multitronic 8 speed.

vass994 · Mar 11, 2022

KRUTO said:
Thank You very much. I got this problem on my Audi A4 B8 2.0 TDI 105 kW CAGA, 8 CVT. Before I found this topic, I changed water pump, engine termostat, nothing changed. Then I change only termostat on that hose, nothing changed. When I change all that hose (in image - part number 23), problem is solved! Thanks man!

Nobody in Bratislava (Slovak Republic) can solved this problem. In Audi service they said - this is normal with that engine Then I found Your topic. You saved me, You saved my car Many thanks again!

HI
In what direction should be the thermostat pointed

keko12 · Mar 18, 2022

I had the same problem . This forum helped me to identify the problem . I changed the thermostat but the problem was not resolved. I have changed this one there on photo with identification code 1K0121113A and now everything its ok . The temperature on the car have to stay always 90 °c . Thank you guys, you saved me a lot of money .

Sent from my SM-A525F using Tapatalk

dcheng · Mar 23, 2022

keko12 said:
I had the same problem . This forum helped me to identify the problem . I changed the thermostat but the problem was not resolved. I have changed this one there on photo with identification code 1K0121113A and now everything its ok . The temperature on the car have to stay always 90 °c . Thank you guys, you saved me a lot of money .

Sent from my SM-A525F using Tapatalk

I have the same problem with my A6 2.0 TDI 177 (CGLC) engine - very hard to hit four dashes on coolant temp gauge and temperature drops when car is going down hill. I changed the main thermostat 2 weeks ago but problem did not go away. Now I am planning to change the EGR's thermostat (1K0121113A), but I am not sure if that will indeed solve the problem for me. I know for keko12 that solved the problem, however I have also read in other forums that members changed both thermostats to no avail.

Some people, including my local Audi dealership, say it's normal for diesel engine to warm up slowly, be affected by cold weather, or looses temp when not under heavy load. But when I first purchased my car 10 years ago there was no such issue. My brother's Q5 has the same CGLC engine with the difference being quattro and S-tronic, and his car does not have the issue I have.

I logged the Q5 and my A6's coolant temp(G62) and radiator outlet temp(G83) using VCDS. I notice for Q5 the coolant temp will hit 90C after 15 minutes of driving and radiator outlet temp remains at 40C and won't hit 60C until after 40 minutes of driving. However for my car both coolant temp and radiator outlet temp increase together after engine start, and after 45min/30km of driving, coolant temp only hits 76C and radiator outlet temp fluctuates between 50 and 80C.

Could the problem be caused by EGR thermostat stuck open? Cheers.

BFleming · Apr 11, 2022

I will chip in with my recent experiences... 2012 B8.5 2.0TDI CAGC (177 Hp). It never got up to temperature, sitting at 75C when warmed up. I bought a Gates thermostat, fitted it (blood, sweat and tears mostly thanks to that push-fit pipe that wouldn't separate) last weekend, filled it with coolant and took it for a test drive. One thing became immediately obvious - it was no better - worse actually as the temperature now fluctuated depending on speed etc. So I went back and tried to bleed the system properly. Now there's a lot of info online on how to do this, but this way worked for me...

Coolant reservoir cap removed, and engine running.
Removed the scuttle panel (in front of the wipers) which took 1 minute.
Found the coolant hoses going to the heater core.
The left one (looking at them from the front of the car) had a funky pattern printed on it, and a small pinhole in the middle of that pattern. I slid the hose off enough so that the pinhole allowed air to escape the system - which it did, followed by a stream of coolant!
Tightened everything back up, set the coolant level in the reservoir, put that cap back on, and took it for a test drive - and it got up to 90 & stayed there.

I did 600 miles in the car this weekend, and it was faultless.

dcheng · Apr 13, 2022

BFleming said:
I will chip in with my recent experiences... 2012 B8.5 2.0TDI CAGC (177 Hp). It never got up to temperature, sitting at 75C when warmed up. I bought a Gates thermostat, fitted it (blood, sweat and tears mostly thanks to that push-fit pipe that wouldn't separate) last weekend, filled it with coolant and took it for a test drive. One thing became immediately obvious - it was no better - worse actually as the temperature now fluctuated depending on speed etc. So I went back and tried to bleed the system properly. Now there's a lot of info online on how to do this, but this way worked for me...

Coolant reservoir cap removed, and engine running.

Removed the scuttle panel (in front of the wipers) which took 1 minute.

Found the coolant hoses going to the heater core.

The left one (looking at them from the front of the car) had a funky pattern printed on it, and a small pinhole in the middle of that pattern. I slid the hose off enough so that the pinhole allowed air to escape the system - which it did, followed by a stream of coolant!

Tightened everything back up, set the coolant level in the reservoir, put that cap back on, and took it for a test drive - and it got up to 90 & stayed there.

I did 600 miles in the car this weekend, and it was faultless.

Thanks for sharing your experience, BFleming. Did you take a picture of that left coolant hose? I wonder what it looks like. How did you stop more coolant from shooting out of the pinhole? I don't have much experience working with things under the bonnet, but I am very tempted to take out the EGR thermostat (1K0121113A) to see if it is stuck open. To do so, do I have to drain out coolant? I am guessing I have to. Then I will have to refill the coolant. Do you know the proper way to do it? Especially when one needs to make sure there is no air trapped inside the cooling system.

Daveabuk · Apr 13, 2022

Just my input again on this. I have changed both the EGR thermostat and main thermostat with genuin parts from TPS and still struggle to get to 90 and maintain with the heaters on.

I pulled this matrix pipe with the bleedhole today with the engine off and immediately it shot coolant out which tells me it's already bled.

Currently at the end of my tether now. I'm totally lost for things to try. The only other thing to do is to replace my EGR valve with a genuine one as that's the only aftermarket part on my engine at the moment.

I have also tested both the old EGR and engine thermostats with a thermometer in a pan of water and watched it with my own eyes start to open at 75c and 87c respectively.

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