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1.9 Tdi Temps Running Cold(slow speed driving/city driving)

Discussion in 'A4/A4 cabriolet/S4 forum(B6 chassis)' started by Eoghan, Feb 8, 2010.

  1. Eoghan
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    Eoghan New Member

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    Has me very confused this one...Every since i got the car its all ways seem to run a bit cold never reached 90 allways stayed about 70...So changed the thermo stat last week and no change..So then today changed the coolant temp sensor still the same..Water pump was changed about 10k ago also...Basicly the car will reach 90 on a motorway or once the speed is a constant say 60 to 70mph and stay at 90 but once you start to drive in say city traffic of lower speed around 30mph or slow speed traffic the temps drop down to 55 to 70 degree's....Anyone seen this happening before??Fan seem to be operating fine too not seized etc...Not much else i can think of really.Its a 100bhp 2002 AVB engine a4...

    Cheers Eoghan
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  2. Mike B
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    Mike B Member

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    Our 2002 TDI130 sport does this too but heating etc seems fine so not to worry about the temp maybe the gauges are inaccurate?
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  3. Jason-Con
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    Jason-Con Member

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    ditto. seems to be a common fault.
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  4. simon.m
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    simon.m Active Member

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    my tdi did that and was not getting to 90 so had the temp sensor and stat changed it now gets up to 90 but just if im driving it evan around town still gets to 90 but after 2 miles or so of stop start trafic.
    but if i just sit there on tick over it gets warm ie heating but dont move the gauge much. thinking its ok just in the cold
    and the viscus fan running all the time plus us pinching the heat too its doing the best it can haha :think:
    Last edited: Feb 9, 2010
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  5. Eoghan
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    Eoghan New Member

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    Nope temp guage not inaccurate checked it today in work and guage reading 70 and the actual reading was 68.8 so fairly close....Cant really think its normal because some times it will go down as far as 50 degree's...Seems to take ages to warm up too,drove home from work today and its a 10mile drive and only reached 70ish....

    Cheers Eoghan
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  6. simon.m
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    simon.m Active Member

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    im told the tdi`s do take longer to get hot so i dont think there is to much of a problem there.
    did you try with the heater off or on low to see if it gets up to 90 faster ? did you have it stuck on a fault finder as it maybe the temp sensor
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  7. quattrojames
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    quattrojames Moderator Staff Member Moderator

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    Aren't there two coolant temp sensors on A4's?
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  8. simon.m
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    simon.m Active Member

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    i think so hold on ill look
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  9. simon.m
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    simon.m Active Member

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    in the book it has many temp sensors but seems only one for coolant or so i can find
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  10. vinesh
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    vinesh Member

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    Mine was doing the same after changing the thermostat - there was an airlock.

    I squeezed the bottom rad pipe to release the airlock.

    My car sits at 90 now :)
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  11. simon.m
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    simon.m Active Member

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    how long does it take to ge to 90 vinesh
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  12. quattrojames
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    quattrojames Moderator Staff Member Moderator

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    I think you're right, not sure where in the recesses of my mind I dragged that up from!
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  13. simon.m
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    simon.m Active Member

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    i thought there was more than one too but cant find it but there is about 5 plus for the temp ie petrol and so on
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  14. vinesh
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    vinesh Member

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    around 10-15mins
    It then stays at 90 for both city and motorway driving
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  15. Eoghan
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    Eoghan New Member

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    No faults at all did a scan today,work in a Audi maindealer and even the head mechanics and my foreman are puzzled about it...Usually you would expect it to overheat in traffic if anything not go cold...
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  16. Eoghan
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    Eoghan New Member

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    Only one in mine..4 pin green coolant temp sensor..
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  17. simon.m
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    simon.m Active Member

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    sems the same as mine im thinking its just as its so cold out there as i no my car is ok
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  18. simon.m
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    simon.m Active Member

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    im thinking if you could turn the viscus fan off that would help as it really dont need it in the winter.
    but saying that i dont think iv ever had my main fan kick in. not evan in the summer as it never really got over 90 maybe they just run colder than what we are used to ie the vax hal i had was always getting hot evan in the winter.
    Last edited: Feb 10, 2010
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  19. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    Sounds like you need to replace the thermostat.
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  20. simon.m
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    simon.m Active Member

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    iv had both done last week so ill not no till summer if it heats up to kick the fan in.
    its getting up to 90 fine now just not over it but would think it would not any way as its cold out
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  21. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    The guage should come up to 90c and stay there in normal driving.

    The dials have a buffer built in so any temp within the normal range, shows exactly 90c.
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  22. simon.m
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    simon.m Active Member

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    thats what min is doing so im thinking its ok
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  23. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    Just shows you how Main Dealers are useless.

    A diesel engine, when ticking over, tends to cool off naturally. Unlike a petrol, a diesel running at idle is running extremely lean, and the large intake charge means the EGT's are low and the thermal output is low. With a working thermostat, at idle the stat would close, and the water would only be circulated round the block and heater circuit, which should generally mean the engine stays at 90c. If you've got the heater on full bore, then it might cool off a little, especially if its very cold outside.

    If however the thermostat is duff, it wont properly close, so the main radiator will continue circulating water, and the engine will cool off far too much, resulting in the low temps. Its also likely the engine will be running cold even when in normal driving as the stat is allowing too much water thru the radiator.
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  24. vinesh
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    vinesh Member

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    it should always stay at 90.
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  25. simon.m
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    simon.m Active Member

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    think that cleard that up nicely thanks aragorn
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  26. Eoghan
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    Eoghan New Member

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    New thermostat fitted last week so aint the problem..And yes a diesel does run colder but not to the point when the needle hit's 90 and then drops off back to 50 sitting in traffic..So doesnt really make maindealers usless now does it??
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  27. adamss24
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    adamss24 Well-Known Member

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    Eoghan, i would change the viscous fan first as it looks to me that its faulty. When the engine is cold, you should be able to stop it with a rolled newspaper and be dificult to stop when engine is fully warmed-up ! I do hope you fitted a new genuine thermostat as i got some aftermarket ones wich open much early and some were sticky so would not close(thats why they are soo cheap). Thermostats are a fail safe design and when duff, they will stay open and allow water to circulate trough the radiator's core...
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  28. simon.m
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    simon.m Active Member

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    is there not a wier you can pull apart for the viscous fan ?
    and how do you no if viscous fan is faulty i would have thought it would not work.
    i can stop mine when its cold by hand is that good or bad i dont no hahahaha
    Last edited: Feb 11, 2010
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  29. Eoghan
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    Eoghan New Member

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    Removed the fan and drove it still does the same and temps still drop off as quick...The thermostat is genuine and not stuck open..Bottom hose gets warm but not half as hot as the top one so im guessing the thermostat is opening and then closing as the temp drops off....
    #29
  30. simon.m
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    simon.m Active Member

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    i had mine on tick over for 20 mins today in the snow the guage did not move but it was toasty in the car as soon as i drive off
    up it goes to 90 its strange but im starting to think its not a problem.
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  31. Mike B
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    Mike B Member

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    The stat may be at fault if the gauge is right.The only way to know would be a swop with one which has proved itself in another car .Is it worth the trouble?Are they still wax based and are they tested in manufacture?Once upon a time we used to have winter and summer types and I recall that they all performed differently due to the crude technology.
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  32. simon.m
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    simon.m Active Member

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    i hope its not the stat iv just had a new one from audi
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  33. lewis.bates.73
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    lewis.bates.73 Member

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    i have the the exact same problem I need to know will this stop my fans working and cooling the engine down or not because I've got to go London today and I don't want it to overheat thanks
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  34. Bobo
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    Bobo New Member

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    I have the same problem on my Audi A3 1.9tdi, i have changed the thermostat and the temp sensor, but nothing positive was happen.
    Cold air from the vents for very long distance, even if the car is not moving, but i have realized if the car its not moving, and the heater its off, the gauge temp its moving faster (maybe hour for 90, huh) :))...I REALLY dont know what to do anymore, I'm thinking to change the thermostat again, but first I would like to check the blower and the area around the blower...I have no clue anymore...friend of mine from Audi said that there is the same problem with every Audi or Volkswagen (1996-1999 model) with climatronic, but why, i dont know
    If someone have the solution, please be kind, and share with us (frozen :))
    #34
  35. lewis.bates.73
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    lewis.bates.73 Member

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    Mine is the same and i have a seat leon 1.9tdi that does exacly the same so must be common on these engines even though ive changed the temp switch on both and the thermostat so i dont know but ive had no other problems for example head gasket or anything so must be fine lol
    #35

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