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Expansion tank issue

Discussion in 'A4/A4 cabriolet/S4 forum(B6 chassis)' started by niftyandy, Jul 21, 2009.

  1. niftyandy
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    niftyandy Member

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    [Jul 21, 2009]
    Hi

    Silly ar*e that I am, I unscrewed my expansion cap at the weekend with a view to topping up the tank as it was lightly low....but got distracted and forgot to top up and more importantly forgot to tighly screw the top on....it was just loosly on with perhaps 2-3 full rotations left before being tight. Anyway when driving up the M6 at about 80mph I got the red coolant warning signal....and the water temp went very north!

    Water was everywhere and the expansion tank was growling and hissing from the pressure valve underneath as the water pressure had dropped causing the coolant to boil...expansion tank was hissing like a kettle! At least I know the cause...ahem, Me!...

    Anyway...I've topped up the expansion tank about 6 times now for the last 3 days and its still boiling away whenever I push on...if i drive very carefully I can perhaps get 20miles before the temp needle rises and I get the coolant signal again.

    Ive been driving for a few minutes/miles trying to get the expansion tank coolant circulating but to no avail...it always seems to boil eventually...sometimes further than other times before it happens?

    Is the problem that i just haven't got enough coolant into the system and there's still not enough pressure there and/or I'm driving too far before checking the levels again thus causing the boiling?

    Does anybody know the official procedure to refill the coolant system via the expansion tank...ie how long to run the car to get it circulating? how long to leave the car before topping up etc....What's the capacity of the cooling system?...anybody know?

    I've got a 2004 3.0Quattro Cab...

    Cheers for info!
    Andy
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  3. technics100
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    technics100 Member

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    [Jul 21, 2009]
    I recently flushed and refilled the coolant system on my 4.2 S6. I drained the coolant from the bottom of the radiator (drivers side) and also from the engine block. Then refilled it. I turned the A/C up full and on full heat then let the car come upto temperature I think the cars needs to get to about 90c to let the thermostat open. it should guzzle some coolant and then just keep topping it up. Mine took 11 litres from empty..
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  4. niftyandy
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    niftyandy Member

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    [Jul 21, 2009]
    Hi
    Thanks for the info matey...

    ....but did you do this refilling (of the tank) once it had gulp some fluid, with the expansion tank cap off ?

    I've been doing this with it on, then letting the engine cool down again before retrying the process....so as you can imagine its taking ages as, as soon as the engine is hot its getting upto pressure then I can't take the cap off or I'll end up in the local burns unit!

    I was under the impression that it needed to be on to get the pressure to force the circulation around the block.

    if not then I'll try just adding as necessary once its upto temp with the cap off.....much easier!....as long as it doesn't boil too much !!
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  5. technics100
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    technics100 Member

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    [Jul 21, 2009]
    I filled it while running and cap off, I actually revved the car while standing with the heaters on full and it gulped some coolant down.. check your heaters are blowing hot air, if not you have an air lock in the heater matrix.. I think having the heaters on draws the heat from the coolant..
    #4
  6. pjmspeedy
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    pjmspeedy Dude, what's mine say ?

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    [Jul 21, 2009]
    I did this only a few weeks ago like a muppet!

    I pulled up on the drive and the temp needle just went past 90 and I thought that's odd as it's never gone past that! then saw some steam coming from under the bonnet so I quickly boiled the kettle and topped it up then left it over night.

    The next morning I started it up and took it round the block for it to get up to temperature then went back home let it cooled down then topped it again.

    It's been fine since then!
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  7. niftyandy
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    niftyandy Member

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    [Jul 22, 2009]
    Hi again

    I think my expansion tank was damaged internally when it initially boiled over....its the only weak link in the chain...tried a mates VW Golf tank cap (same part no!)...same result so it wasn't the cap!

    I did a head gasket check this am....i.e. released cap to release any pressure in the coolant system, put cap back on then started it up for 90seconds from stone cold....then turned off motor and checked for coolant pressure....no worries there I feel as there was no air pressure release....did it again a few minutes later and still nothing so deffo not a head gasket failure. Apparently if there is a head gasket failure then the motor's compression would leak into the coolant system thus raising the pressure before the coolant system has had a chance to heat itself up thus raising the pressure!

    New tank and cap on order from Audi....£18.18 incl vat for both!

    Andy
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  8. joylee
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    joylee New Member

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    [Aug 10, 2009]
    It is indeed the expansion tank that has a problem, and it needs to be replaced immediately.
    _________________
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    Satisfaction is derived from a job well done.
    Expansion Tank Replacement
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  9. diagnosticator
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    diagnosticator New Member

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    [Aug 18, 2009]
    Make sure you bleed all the air out from the bleed screws , without the engine running. Then top up the tank as needed and with the cap loose, start the engine and run up to 2000 rpm for several miniutes. Then let the engine idle with the cap loose until the fan starts up at least once, then top up as needed and tighten the cap.
    [​IMG]
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  10. CMD
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    CMD Pointing Forward's!!!!!!!!!

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    [Aug 18, 2009]
    Nifty you will have to bleed the system find your's it might be plastic type screw

    undo this screw to let any air out of the system after car is at normal temp ,use a rag to catch any coolant once you have opened the bleed screw ..One the 1.8t the bleed screw is made of plastic and some time's snap's in two when trying to undo so just be carefull.Good luck
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