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is it the thermostat you think? soz long post lots of info

Discussion in 'Diesel forum' started by swarcup, Oct 14, 2009.

  1. swarcup
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    swarcup Well-Known Member

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    [Oct 14, 2009]
    now then folks

    trying to fathum out an issue

    have a 2001 2.5 v6 tdi sport quattro 180, engine no ake

    temp guage sits at around 65 -70 degrees in normal driving conditions and i know it should be 90 degrees.

    i changed the temp sensor and it made no difference so i had a code read and it refered to temp guage short to earth which would mean a fault on the guage itself.

    BUT when i am towing or accelerating hard you know giving it a bit of pasty the needle will rise and sit at 90 like it should. the engine obviously will generate more heat due to the extra effort its doing.

    if the thermostat is opening to early or is stuck open slightly will the temp guage show this like it is. does a thermostat open and close all the time your engine is working, i.e. it opens at 90 and diverts water to the rad but when the rad has cooled the water does it close again untill the water is at 90 again.

    there is another sender on the bottom rad hose, i think this controls the fans though is it worth changing this also,

    last bit of info there is a fan constantly running i think it is supposed to be, and behind that is another fan that comes on and off should this fan be always on as i think that is the reason that when idling or driving normally the temp drops as this is cooling the rad.

    if the thermostat is stuck open and water is always ciculating through the rad then this fan is cooling the water when is shouldnt be do you see.

    if anyone has had this issue before and can help out or is a wizzo tech i will be a really happy person ( until the bill arives for the replacement of the thermostat,cam belt,waterpump arrives) lol
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  3. adamss24
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    adamss24 Well-Known Member

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    [Oct 14, 2009]
    Hi mate, thermostats are quite a common failure on the v6 tdi engine and as you know, its a belt off job. I would check first the electrical issue you have with the temp. sensor and replace the thermostat when funds allow. If the car its high milleage, i suggest you replace the hydraulic damper next to the cambelt tensioner, bit pricey but they fail with high mileage. If you are not that far away from London and fancy a ride, i could have them bits replaced for you. It would cost about 400 quid wich will include full cambelt kit, tensioners, rollers, pump belt, injector belt + tensioner, aux. drivebelt, KWP/Meyle water pump with metal impeller and 5L of g12 antifreeze + computerized setting of the diesel pump/ diagnostic test. Try and price all this at your nearest garrage...
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  4. swarcup
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    swarcup Well-Known Member

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    [Oct 19, 2009]
    wow thats a superb offer! :icon_thumright:

    unfortunately i dont live in the london area but 250miles north in east yorkshire
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  5. adamss24
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    adamss24 Well-Known Member

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    [Oct 19, 2009]
    Time to visit forgotten relatives down south ? Cheers...
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  6. swarcup
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    swarcup Well-Known Member

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    [Oct 20, 2009]
    WISH I HAD SOME

    If i do il message you, will you be able to all this in 1 day or would it be a stay over job
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  7. adamss24
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    adamss24 Well-Known Member

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    [Oct 20, 2009]
    I need 6 hours minimum as its a fairly involved job and sometimes bolts are rusty and they might need soaking in wd40 but the job does not take longer than 8 hours ! I ussualy have troubles with the viscous fan as they often stuck fast and you cannot put heat on it without dammaging the bearings. Belt only takes 15min to put on the rollers, its getting at it that takes time ! Cheers, Chris- 077 899 12128.
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  8. swarcup
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    swarcup Well-Known Member

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    [Oct 23, 2009]
    adamss24 just to pick your brain

    ive been told that it is unlikely to be my thermostat because it doesnt overheat when towing, the guage rises to about 90/92 then drops and sits nicely at 88 as if the thermostat is opening at the correct temp and if it was stuck open it wouldnt get any temp at all, but it is getting quite warm , now you may correct me on this, but if this is so i am thinking the most obvious reason should be the viscous fan.

    not to sure how these work, should it be on instantly the moment the car starts or will it come on when the coolant warms up, i know the speed varies according to the coolant temp, is there any way by spinning it you could tell if it is not disengaging etc.

    im sort of thinkin its providing to much cooling when driving normally

    cam belts not due for another 20,000 miles. :banghead:
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  9. adamss24
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    adamss24 Well-Known Member

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    [Oct 23, 2009]
    Thermostats are designed to stay open when they fail... You could try holding the viscous fan with a wrapped newspaper when its cold that should stop spinning right away. Its gripping more when the engine is hot so it will be difficult to stop when hot if its working fine. Very few fail though... The v6 tdi wont overheat even without the viscous fan as the aux/electric fan should cut in. They only overheat if there is a head gasket failure or the impeller on the watter pump falls off. I wont trust the gauge too much as what you see on the dash is miles apart from what the engine is doing so the right temp could be off with about 20 Celsius...
    Last edited: Oct 23, 2009
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  10. fjtwelve
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    fjtwelve Moderator Staff Member Moderator

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    [Nov 3, 2009]
    Had the same problem. I'm afraid it was the thermostat, the problem disappeared after. Had mine done when i had the belts done. 400 quid is startlingly good. Over 20,000 miles. If you can get another 3-4mpg due to the engine running better it'll pay for itself over 20000miles, and my mpg perked up a couple even though it has subsequently been found the injection pump is knackered.
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  11. swarcup
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    swarcup Well-Known Member

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    [Nov 5, 2009]
    thanks for all your help il look into getting it done with you adams24 after crimbo if you will still give me that price. i will give you a call after crimbo :thumbsup::thumbsup::thumbsup::thumbsup:
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