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Strange temp problem advice please

Discussion in 'A3/S3 Forum (8L Chassis)' started by macpdm, Nov 18, 2011.

  1. macpdm
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    macpdm Member

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    [Nov 18, 2011]
    Afternoon all

    Would very much appreciate some of that superb assistance again.

    Just had the thermostat changed in my car as the car just wasnt getting hot enough. Prior to this I changed the temp sender and when this didnt resolve it decided to get the stat changed too.

    So the mechanic has just called to say he has replaced the stat but everytime the car gets up to around 66 degrees the fans kick in for 10 seconds and drops the temp back down again and they are coming on about every 30 seconds. We are a little stumped anybody have any ideas ?

    Thanks again in advance.
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  3. camscockle20vT
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    camscockle20vT The stigs ugly brother

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    [Nov 18, 2011]
    Hi mate, a friend of mine had a cupra r that had this problem, he had a water pump failer and was informed there may be broken plastic from the propeller still floating around even though he had new coolant, he wasnt happy with this so took it to a specislist that said it was possibly a dodgy ecu problem. He never fixed the problem and just got shot of it. Hope you solve this problem tho dude.
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  4. Westy
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    Westy Double Dark Side! Diesel & 8P

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    [Nov 18, 2011]
    bit strange mate.

    Does the water temp ever reach 90 degrees on the inside guage? If not I would unplug the fans to stop them kicking in and then see if the temp actually reaches 90. If it does then you know the stat is opening properly and isn't at fault.

    In VCDS you can check all temps and see when fans are kicking in and things like that which would be helpful if your mechanic has VCDS.

    The fans shouldn't kick in until 100 degrees so maybe you have a dodgy fan switch!
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  5. macpdm
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    macpdm Member

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    [Nov 18, 2011]
    Thanks guys

    Yes it is very odd in that with the new stat in and the AC off it reaches 90 on the guage and stops then both fans kick in at 103 according to his diagnostic comp. he also does not think there is anything wrong with the water pump impellor as the cars heater gets perfectly nice & toasty and having done an A3 with a busted impellor he would expect it to run cold which is what he has found before.

    He thinks it could be the fan control unit under the battery which sounds expensive.
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  6. valentn
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    valentn Member

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    [Nov 18, 2011]
    You might have the wrong temp sender, when I went to the Auto parts supplier he asked me which one I needed, one with a blue or yellow top, as it differes from cars with AC and non-AC. Do not know if that would cause it but might be worth a shot.
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  7. macpdm
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    macpdm Member

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    [Nov 18, 2011]
    Thanks anyway but im confident the green temp sender I have installed is the right one as it seems to be reading correctly last time we checked.
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  8. Westy
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    Westy Double Dark Side! Diesel & 8P

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    [Nov 18, 2011]
    Yeah it is normally a green one.
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  9. Welly
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    Welly VX220 SC Driver :)

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    [Nov 18, 2011]
    A broken water pump would be obvious, you normally get water coming out of the header tank when the cap is off as it simply doesn't circulate.

    The fans will be on with the air con on, one of them should run constantly.

    Not a simple one this, very strange.
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  10. macpdm
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    macpdm Member

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    [Nov 18, 2011]
    No your right but not noticed any water overflowing from the header.Just picked it up and drove home about 2 or 3mls with AC off then I sat with it idling for 3 or 4 mins and it was reaching 90 and no fans kicking in.

    So the fans will run with the AC on but one runs constantly ?

    I think I will do a full coolant flush never done it before though so any pointers are welcomed ?
    Last edited: Nov 18, 2011
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  11. macpdm
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    macpdm Member

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    [Nov 20, 2011]
    Just an update Ive been using the car for a couple of days now and took a long drive today with a mix of motorway as well as A & B roads and the guage went to 90 once warm and stayed there rock steady. Im hoping this means all is well but im changing the coolant tomorrow morning just to be certain and i think it should be done anyway.
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  12. s4mark
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    s4mark Member

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    [Nov 20, 2011]
    very strange mate but fingers crossed its sorted itself for u
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  13. stevie e
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    stevie e Member

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    [Nov 20, 2011]
    remember to bleed system ,with ac on ,49c to check temperture
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