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Thermostat issue?

Discussion in 'A3/S3 Forum (8L Chassis)' started by ROBS3, Dec 17, 2009.

  1. ROBS3
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    ROBS3 Member

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    [Dec 17, 2009]
    I’ll try and keep a long story short...

    Basically, about 5 months ago my dash temp gauge was playing up a bit, taking longer than normal to get to 90˚ (if at all), then on faster journeys (motorways) it would dip, then when sitting in traffic it would go back up again. Previous to this it would get to 90˚ and would stay there.
    After doing a bit of research it pointed to a faulty thermostat. So took it to the garage (Audi specialist) who said it’s unlikely to be the thermostat and did a few tests – and according to the 'laptop' it was ok, and said that it isn’t unordinary for the gauge to do this (not according to my research!)
    So left with the same problem.

    Still not happy with it, I took it back and asked for it to be changed anyway. So thermostat was replaced, left and everything was perfect – getting to temp ok and staying there. Phew!
    Until a couple of weeks ago, the problem came back. Took it back, once again – the 'laptop' says it’s ok, and was told that it could possibly be a faulty gauge, which would require a new dash costing about £400!
    Now after more research the symptoms certainly don’t seem to point to a faulty dash? I think it must be another faulty thermostat.

    Can anyone give me some advice, or may have some knowledge on this? I don’t really fancy having to take it to another garage and having to pay £££s for someone else to look at it, when I’ve already paid for it to be sorted.

    I've also tried the climate control 49 temp display trick. When on the motorway displays mid 70's, in traffic and stationery anywhere between 80-90. Basically follows a similar habit as the gauge, although the numbers are slighly different. Just out of interest what should be at?

    Any advice or help would be much appreciated.

    Cheers
    Ps had the coolant sensor replaced a couple of months ago, and the water pump is only a couple of years old if this helps?!
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  2. 666markyboy
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    666markyboy Well-Known Member

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    [Dec 17, 2009]
    I think it's just down to the weather mate.... mine is giving exactly the same kind of readings... i too ran the temp via the aircon display on the motorway journey home tonight and it never hit 70.... 68 pretty much all the way home till i got off the motorway then it rose a bit more.... i'm thinking of blocking off the radiator grill with some ally sheet just to reduce the airflow a bit in the winter months as i remember it was the same last year but has been fine in the summer
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  3. S3KO4
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    S3KO4 Member

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    [Dec 17, 2009]
    mine give 95C and on the dash is 90C. could be another faulty thermostat, or temp sensor.
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  4. ROBS3
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    ROBS3 Member

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    [Dec 18, 2009]
    Thanks for the input guys.
    I hope it is the weather - but saying that, I don't remember it happening during previous winters.
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  5. pauldazzle
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    pauldazzle Active Member

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    [Dec 18, 2009]
    Nothing to do with the weather. Temperature should remain stable in anything other than extreme conditions.
    Testing the thermostat with a laptop is impossible! The thermostat has no electrical components. It's common for thermostats to stick especially if the wrong mixture of coolant has been used, or the dreaded radweld has been used at some time.
    The engine taking a long time to reach normal operating temp is a classic sign of a stuck open thermostat, as is the engine cooling down when at cruising speeds, & warming up again when slower or at idle.
    Very common cause of erratic temp gauge is a faulty CTS (coolant temp sensor), but your symptoms are of a stuck open stat.
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  6. ROBS3
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    ROBS3 Member

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    [Dec 18, 2009]
    Cheers pauldazzle,

    Think I'll be going back again :banghead:
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  7. 666markyboy
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    666markyboy Well-Known Member

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    [Dec 18, 2009]
    I'll pop out for a new stat then tomorrow.... makes total sense when you hink about it...
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