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Necessary to drain the coolant system when changing thermostat?

Discussion in 'A3/S3 Forum (8L Chassis)' started by finesse, Mar 11, 2010.

  1. finesse
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    finesse Active Member VCDS Map User

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    [Mar 11, 2010]
    Evening fellas,

    Apologies if this has been asked before, couldn't find anything.


    Changing the thermostat tomorrow, is it necessary to drain the coolant system when changing thermostat?

    I have some G12 to hand.

    Thanks
    John
    #1
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  3. beachbuggy
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    beachbuggy Well-Known Member

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    [Mar 11, 2010]
    Yes and No.

    When you remove the thermostat the coolant will leak out anyway. If you prefer to do it without it leaking all over the lower half of the engine, then yes drain it out first.

    If you install a new seal on the thermostat then it's best to soak the seal before installing in some coolant. Gives a better seal.
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  4. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Mar 11, 2010]
    Fraid so mate but if you use a clean container to drain it into you can reuse it.

    Note that draining from the drain plug on the bottom of the radiator won't get it out of the block...

    <tuffty/>
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  5. finesse
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    finesse Active Member VCDS Map User

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    [Mar 11, 2010]
    beach and tuffty, appreciate your replies.

    I have just under 1.5litres of G12, would I need some more? If I decide to drain the system..
    Last edited: Mar 11, 2010
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  6. Welly
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    Welly VX220 SC Driver :)

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    [Mar 11, 2010]
    I would of thought that would be fine.

    I would just let the coolant leak that is going to leak when you unbolt the thermo pipe, and top up on completion to be honest. You won't lose it all.
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  7. A3Tom
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    A3Tom Smell my finger.

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    [Mar 11, 2010]
    I reckon you will drop about half of it when you change the 'stat. I didnt bother draining mine...just topped it up and its fine.
    #6
  8. 1animal1
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    1animal1 The Clar!! it mouves!!! VCDS Map User

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    [Mar 11, 2010]
    im doing the A3 on Saturday.....just started to stick and the coolant looks old

    im gonna be draining the system and flushing with the hose pipe, then replace the thermostat and replace with 2ltrs of G12 which is what Audi recommend (arse for selling it in 1.5litre bottles) then top the rest up with water
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  9. Welly
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    Welly VX220 SC Driver :)

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    [Mar 11, 2010]
    LOL, it's blatantly designed that way......
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  10. 1animal1
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    1animal1 The Clar!! it mouves!!! VCDS Map User

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    [Mar 11, 2010]
    fella i cant believe im that unlucky in life that im gonna be doing my SECOND A3/S3 thermostat........ ow bad can it get!!!
    #9
  11. finesse
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    finesse Active Member VCDS Map User

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    [Mar 11, 2010]
    blaaa so much for Audi reliability
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  12. 1animal1
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    1animal1 The Clar!! it mouves!!! VCDS Map User

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    [Mar 11, 2010]
    think you mean so much for our 'gulability'
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  13. finesse
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    finesse Active Member VCDS Map User

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    [Mar 11, 2010]
    Thanks for all help, appreciated much!!

    John
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  14. 1animal1
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    1animal1 The Clar!! it mouves!!! VCDS Map User

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    [Mar 11, 2010]
    no worries, best of luck with the thermo....its an ball ache of a job and wouldnt wish it on anyone :)
    #13
  15. Matt82
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    Matt82 Active Member

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    [Mar 12, 2010]
    when the stat is out.... you dont have any choice whether the coolant drains out or not
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  16. finesse
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    finesse Active Member VCDS Map User

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    [Mar 12, 2010]
    Thanks Matt!
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  17. 1animal1
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    1animal1 The Clar!! it mouves!!! VCDS Map User

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    [Mar 12, 2010]
    you dont but you do have a choice as to how much you end up losing!! thats the defining point here....... also matters how long you take to refit the new one
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  18. finesse
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    finesse Active Member VCDS Map User

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    [Mar 12, 2010]
    Sounds like a game of cat and mouse :D:D
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  19. Matt82
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    Matt82 Active Member

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    [Mar 12, 2010]
    sounds like picking peanuts out of dog poo. its coolant. its not dear and changing a stat isnt a case of life and death, i dont get why its such a drama to you lot

    buy a new stat. buy a new seal. buy another bottle of g12, because youre always gonna need it anyway.

    get the stat out. if you really care about losing coolant, get the new stat in quickly. its still going to trickle out until you get the seal/flange bolted back on.

    add the antifreeze in an approximately 50% ratio with water. anything over 30% is overkill anyway so it doesnt need to be precise
    #18
  20. 1animal1
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    1animal1 The Clar!! it mouves!!! VCDS Map User

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    [Mar 12, 2010]
    tis not a problem sir....just looks like a post from you stating the obvious matey

    the post asks do you need to drain the system...no you dont, although you will lose most...tis not a rpoblem, tis semantics :)
    #19
  21. Welly
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    Welly VX220 SC Driver :)

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    [Mar 12, 2010]
    ^^^ what he said! LOL :)
    #20
  22. jonny87
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    jonny87 Active Member

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    [Mar 12, 2010]
    i drained my system whilst changing the stat for two reasons, one i didnt want it going all over my block n making a mess of my mates garage floor, two it makes sense to do coolant flush at the same time as doing stat and sender, then you know all is well in there for at least another 12 months
    #21

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