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Could this be a thermostat problem

Discussion in 'A3/S3 Forum (8L Chassis)' started by dan77, Mar 2, 2009.

  1. dan77
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    dan77 dan77

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    [Mar 2, 2009]
    hi all i was driving down the motorway the other day when i noticed my engine temp had dropped about 10 degrees, i kept an eye on it for the rest of the journey and it kept goin up and down really slowly, this makes my limited little brain think it might be the thermostat reacting slowly, does this sound right to any1, or am i talking out my arse and should i get a garage to have a look!? any ideas would be appreciated
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  3. Mr.G
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    Mr.G Active Member

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    [Mar 2, 2009]
    When my Thermostat was faulty it threw a fault in Vagcom.

    I'd get it to the garage to looksi, can't be a bad thing even just to check it over. Was it cold on the morning in question??

    G
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  4. ash_pearce
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    ash_pearce Member VCDS Map User

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    [Mar 2, 2009]
    there is another thread on here somewhere about thermostats, generally it seems most people's stay around 90 degrees, however if your on the motorway the airflow is greater through the radiator which would lower the temp a bit. To be honest until the temp goes the other way I personally wouldn't worry too much.
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  5. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Mar 2, 2009]
    Prior to me changing the cam belt and water pump over christmas, mine always stayed at 90 deg.... since then its sat at 80 deg occasionally creeping to 90 deg but would then go back down to 80 deg again.

    I am going to change my thermostat in the next week or so, I'll post the results here....

    For the record I have already changed the temp sender (green top)

    <tuffty/>
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  6. dan77
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    dan77 dan77

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    [Mar 2, 2009]
    thanks guys, its booked in for a cambelt change and service next week do you think its worth gettin the thermostat done then?
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  7. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Mar 2, 2009]
    prob wouldn't hurt... the part is about £15 from Audi but not sure what they would charge to fit, you may be able to negotiate a good price as they will have most of the car apart for the cam belt
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  8. Yaz
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    Yaz Member

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    [Mar 3, 2009]
    I would mate, if you're changing the cambelt then you should also change the water pump and in turn the coolant, so it would make sense to change the thermostat at this time...
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  9. Nilz
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    Nilz Defo worth the wait :)

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    [Mar 3, 2009]
    Yep, get it all done at the same time, they going to have the front end off anyway, so might as well.
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  10. A3Tom
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    A3Tom Smell my finger.

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    [Mar 3, 2009]
    Hello,

    First post here so hi!..... I'll do an introduction very shortly.

    My A3 had the same problem, the temp guage was up and down and wouldnt hold at a constant reading. After a bit of digging I worked out it was the temp sender unit, cost about £12 to change and sorted the problem out straight away.

    My guage would go up as normal and then drop off down, then come back up again. Its an easy fix and wont cost too much. Took about 10 minutes all in to sort out.

    Cheers

    Tom
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  11. Westy
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    Westy Double Dark Side! Diesel & 8P

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    [Mar 3, 2009]
    Your temp should stick at 90 no matter what the temp/weather is like outside. I changed mine in January and it always stays at 90 even over that cold period we had with all the snow and -8 temps.
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  12. ianysm
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    ianysm Active Member

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    [Mar 3, 2009]
    Mine is normally around 90 but drops slightly lower if on the motorway etc

    Is the temp sender the cause of lunpy idle sometimes too?
    #11
  13. wibble111
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    wibble111 needs to scratch the itch

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    [Mar 3, 2009]
    Does anyone know if a dodgy temp sender will log a fault with vag-com?
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  14. Westy
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    Westy Double Dark Side! Diesel & 8P

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    [Mar 3, 2009]
    Not sure about that Ian as I haven't had an issue with my temp sender....... yet!

    If your temp is dropping slightly on the motorway then the thermostat is starting to wear, its just a spring loaded valve. The spring just wears out of the years.
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  15. A3Tom
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    A3Tom Smell my finger.

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    [Mar 3, 2009]
    Mine didnt cause a lumpy idle, it ran as it always does but the guage was a bit part time. It would warm up as usual and then drop to 10c or lower, then pop back up and then back down again. The stat was OK as the fans were kicking in etc when the car was stationary in traffic etc.

    When the weathers cold my car (once warmed up) will always run at 90c.
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  16. enda1
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    enda1 Member

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    [Mar 3, 2009]
    The higher tuned 1.8T engine in the likes of the S3 have a sensor on the thermostat and will show a fault. The normal engine has a standard thermostat
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  17. Westy
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    Westy Double Dark Side! Diesel & 8P

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    [Mar 3, 2009]
    The temp sender will throw a fault but not the thermostat. The thermostat is just a spring loaded valve that opens under pressure from the cooling system.
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  18. dan77
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    dan77 dan77

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    [Mar 4, 2009]
    thanks for all the info guys, i`ll get the thermostat done aswell then, and as if the service and cambelt wasnt gonna cost me enough, it snapped a rear spring yesterday!:mad:
    #17

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