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Audi B8 2.0 tdi CAGA coolant temp problems

Don Mundo Jan 20, 2018

  1. Don Mundo

    Don Mundo Audi B8 Sline Monza Silver

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    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?
     
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  3. Darren92

    Darren92 Registered User

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    Diesels especially in winter will always run colder.
     
  4. Don Mundo

    Don Mundo Audi B8 Sline Monza Silver

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    what about the carbon build-up? or it won't increase due to running on lower temperatures?
     
    Last edited: Jan 20, 2018
  5. KrisKrk

    KrisKrk A6 C6 4F 2010 LeMans Avant

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    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 likes this.
  6. Don Mundo

    Don Mundo Audi B8 Sline Monza Silver

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    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.
     
  7. Retroman

    Retroman Audi A3 2010 Sportback 2.0 TDI 170 (CBBB engine)

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    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:
     
  8. KrisKrk

    KrisKrk A6 C6 4F 2010 LeMans Avant

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    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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  9. Retroman

    Retroman Audi A3 2010 Sportback 2.0 TDI 170 (CBBB engine)

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    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.
     
    Don Mundo likes this.
  10. KrisKrk

    KrisKrk A6 C6 4F 2010 LeMans Avant

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

    Might drop something behind my grille


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  11. KrisKrk

    KrisKrk A6 C6 4F 2010 LeMans Avant

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    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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  13. Don Mundo

    Don Mundo Audi B8 Sline Monza Silver

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    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. Audi_coolant_system_CAGA.PNG
    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.
     
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  14. mladen

    mladen Registered User

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

    Don Mundo Audi B8 Sline Monza Silver

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    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.
     
  16. csaba95

    csaba95 Registered User

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    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
     
  17. DarthVAG

    DarthVAG Registered User

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    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.
    209440720.jpg
     

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