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CTS or Thermostat?

Discussion in 'A3/S3 Forum (8L Chassis)' started by SunnyG, Jul 18, 2012.

  1. SunnyG
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    SunnyG Member

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    [Jul 18, 2012]
    Car doesn't warm up no mother how long you drive it its 1.9tdi 130 and it only just lifts off the bottom after a while, is that the CTS or thermostat?
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  2. Nilz
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    Nilz Defo worth the wait :)

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    [Jul 18, 2012]
    I would say cts, worth doing that first as its cheaper and easier to replace.
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  3. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Jul 18, 2012]
    Its almost never the CTS.

    Change the Thermostat.

    CTS also isnt cheaper, its about 40quid, vs 10 or so for the stat.
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  4. SunnyG
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    SunnyG Member

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    [Jul 18, 2012]
    Okay probably do both then i guess how shall i do a coolant flush as the orange stuff in their at the mo?
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  5. Ads_AudiA3
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    Ads_AudiA3 Member

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    [Jul 18, 2012]
    I'd change thermostat - faulty CTS can also gives out cold / hot start issues. Changing the fluid is simple enough, drain it through the drain point, then fill up with coolant and bleed through until no air bubbles.
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  6. SunnyG
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    SunnyG Member

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    [Jul 18, 2012]
    When you say bleed through? Can you elaborate
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  7. Nilz
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    Nilz Defo worth the wait :)

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    [Jul 19, 2012]
    Oops sorry, got it the wrong way round!!! DOH!!!
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  8. jamieA3
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    jamieA3 Member

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    [Jul 19, 2012]
    Well I have just gotten over this problem. a new thermostat cost me 5.49. sure its a cnut of a thing to get out as the housing is behind the alternator, but i am a utter noob and it took me half hour.

    i say change thermostat mate, they seem to be a problem on the cars. If your anywhere near hertfordshire ill do it with you if you like.

    EDIT.. have you checked the temp through the climate control ? hold recirc + ^ then select 49c, press recirc again and bingo it will show you the genuine accurate temperature. then you will know if its a sensor or thermo
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  9. SunnyG
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    SunnyG Member

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    [Jul 20, 2012]
    Yeah I'm a bit far mate near birmingham and ok i will do that what should i be looking for?
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  10. jamieA3
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    jamieA3 Member

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    [Jul 20, 2012]
    Well if you have climate control, do as i said above while driving/at lights or whatever. if your needle is the same as what is says on the climate control then its the thermo.
    when you change the thermostat ( if u do ) youl need to do this **WHEN ENGINE IS COLD**
    1) take of engine cover + bracket thats attached to dipstick guide (holder)
    2) undo expansion tank cover to relieve pressure in system and the remove the coolant hose from the thermostat housing( just behind the dipstick to the left slightly. replace expansion tank cap and put the now leaking hose behind a hose to hold it upright.
    3) using a socket extension piece with a flexi end and a 10mm socket, remove the 2 bolts holding the thermostat housing to the engine ( very very tricky, heres when i broke dipstick guide)
    4) you will then see the thermostat *** take note of how its positioned and which side the seal is *** remove this and replace with new thermostat and seal
    5) replace housing, hose and make sure all is secure.
    6) with expansion tank OFF, start engine and look closely for leaks while reving the engine ( may need a friend with you ) and squeezing the hose you replaced. this will bleed the system of any air thats trapped.
    7) providing all is ok, there are no leaks, the temps gone up to 90 and all the air is out of the system, replace tank cover go for a test drive but not to far from home. inspect again for leaks. replace engine cover.

    job done. It sounds complicated, its not but it is very fiddly ! you will also need to top up the coolant if you lose a lot
    DO NOT MIX COOLANTS, if its pink stuff you have now ( g12) then only use pink stuff or it will curdle/blob up


    heres what you should have before starting.

    * thermostat with seal
    * coolant + water
    * socket set
    * pliers ( for hose clips )
    * flat head screw driver ( engine cover )
    *allen key set ( small bracket at front of dipstick )
    * new dipstick guide just encase ( you will break it 90 % sure )

    And most importantly, lots of patience


    hope this helps, sorry if its a bit long winded. I just would rather tell you myself than re direct you to a guide that someone else has written.
    I was very nervous about doing this job, I even started a thread asking people to help me ( thermostat help hertfordshire ) but once you do it you will feel great and thats one more thing you have learnt.

    all the best , jamie
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  11. Nilz
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    Nilz Defo worth the wait :)

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    [Jul 20, 2012]
    Whereabouts are you based Sunny??
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  12. vfr800
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    vfr800 Active Member

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    [Jul 21, 2012]
    Just to reinforce what jamieA3 said:

    Get a new dipstick guide - it's only a few quid - and 98.9% it will break. If you break it put a glove over the snapped bit to stop coolant getting in.

    Flush and fill with new G12++ (the pink stuff).

    Note how the old stat. and seal is positioned and refit the same way.

    Oh and the coolant it nasty stuff - don't get any on you and wash spillages away with lots of water - take recovered coolant to the local tip.

    HTH Liam
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  13. SunnyG
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    SunnyG Member

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    [Jul 21, 2012]
    Nilz im in wolverhampton, thats a really comprehensive guide thanks to all but to be honest i think that I'm just going to get it done when i service soon as i haven't got a socket set to hand.
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  14. Nilz
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    Nilz Defo worth the wait :)

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    [Jul 21, 2012]
    LOL...after all that Sunny!! ;)

    If you do get it done, just get both CTS and Stat done at the same time.
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  15. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Jul 21, 2012]
    Why? Its almost never the CTS.

    Diagnose the problem correctly, and change the faulty part. You dont replace the light switch, fuses and every bulb in the car when you pop a sidelight do you?

    Symptoms of a CTS are totally different to the symptoms of a faulty thermostat.
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  16. Nilz
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    Nilz Defo worth the wait :)

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    [Jul 22, 2012]
    I had both go on my old A4, so it could be that, but as said get it diagnosed correctly and who knows you may be ~£40 better off if it is just the Stat :)
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  17. SunnyG
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    SunnyG Member

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    [Jul 28, 2012]
    Had VAG mechanic come down today warmed the car thoroughly had a look over to check the issue, checked CTS temp was fine and working, checked thermostat and both coolant hoses were working he showed both with flow once car warmed up, but doesn't understand why recirc and ^ at 49 degrees came up with 30 degrees? anyone understand and care to think why? also saw the issue as not thermostat or cts but the instrument panel being faulty.
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  18. SunnyG
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    SunnyG Member

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    [Jul 29, 2012]
    ??? anyone
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  19. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Jul 29, 2012]
    are you saying that channel 49 on the climate only ever showed 30c?

    Could well be the CTS, but you need to do some proper diagnostics, leaving a diesel idling for a long time is pointless as they run so cool.

    Heres what to do. Get channel 49 up on the climate, and go DRIVE the car. If you have vagcom then connect that and get it to display the coolant temp from the Engine controller as well so you can compare them. Dont go onto a motorway, or any other fast roads, find somewhere around town where your constantly accellerating and braking, so you can get some heat into the system, and keep an eye on the climate display.

    If it just sits at 30c and never moves, then the CTS is likely faulty.

    If it starts to climb (even if it doesnt actually get to 90) then make your way to a faster road, and sit cruising at 50-60mph and see what it does, if it drops back down again, then your thermostat is the likely culprit.
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  20. SunnyG
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    SunnyG Member

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    [Jul 29, 2012]
    Climate only shows 30 once showed 23 rising to 30 on a start up, i haventgot vag com but when the car was on the diagnostic he said the cts was showing 120 something which was normal. So i think its best to do the cts anyway cars getting serviced next week too? Any dangers of driving the car as it is? Effects of driving the car under boost?
    #20
  21. SunnyG
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    SunnyG Member

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    [Jul 31, 2012]
    Did the drive sat at 30 the whole time going to replace cts can anybody elaborate on the above questions?
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