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1.9 Tdi Coolant bleed.

Discussion in 'A6/S6/Allroad forum (C5 Chassis)' started by Iain-A6, Jul 22, 2014.

  1. Iain-A6
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    Iain-A6 Member

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    [Jul 22, 2014]
    Hi,

    I have read the many coolant bleeding ways on the forum, but I am having no luck.

    Firstly the car would not get up to temperature, so I have changed the thermostat. Now the car gets up to temperature, gets the 90 degrees and then drops all the way back down and the temperature gauge wont move. My thinking is an air lock, so I started the car up, heater on full hot and full speed and left it running with the cap off and the heater matrix pipe slightly off.

    After doing this for 40minutes and air bubbles coming out the of the expansion but still no coolant coming out of the bleed hole. I reverted to blowing down the expansion main opening and forcing coolant out of the bleed hole which worked, it also worked when i revved the engine, but on idle nothing would exit the bleed hole.


    Any ideas?
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  3. mrnice
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    mrnice Member

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    [Jul 22, 2014]
    Have you changed the coolant temp sensor?
    Could heater matrix be blocked?
    Filling and bleeding the coolant on mine took about half an hour of very slowly filling while squeezing every coolant hose and raising the expansion tank by 100mm so it sits higher than the bleed hole(crucial).
    I still had to top it off a little after running the car.
    Best if luck!
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  4. Iain-A6
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    Iain-A6 Member

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    [Jul 22, 2014]
    No I haven't changed the coolant sensor, I could get hold of one because it was audi only. I didn't lift the expansion bottle because the screws holding it are stuck. There is a flow through the heat matrix as when I rev the engine water comes shotting out the bleed hole and I get hot air in the cabin.

    I have completely filled mine, so the next plan is to lift the coolant bottle while it's running. It might be ok but, when yours is running is there a constant flow of water out of the bleed hole?
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  5. mrnice
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    mrnice Member

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    [Jul 23, 2014]
    Hi there, I didn't run the engine with the bleed hole open, when filling with exp tank raised coolant dribbled out of bleed hole eventually anyhow. There was no sign of any airlock after at all. I followed the procedure from a Haynes manual for passats (very useful source of info!).
    If you do replace coolant temp sensor remember to order a new plastic retaining clip!
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  6. Iain-A6
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    Iain-A6 Member

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    [Jul 23, 2014]
    Does the thermostat not need to be open? Why do I need a new clip? The current clip is fine and I have removed it several times already.

    The prodcedure is...

    lift the coolant bottle up high, open the bleed hole and just pour in coolant slowly whole squeezing the pipes?
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  7. mrnice
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    mrnice Member

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    [Jul 23, 2014]
    Yup, that's the procedure, then run up to temp and top off coolant to max level, job done. You're lucky (or highly skilled) getting that cts plastic clip off without it shattering!
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  8. Iain-A6
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    Iain-A6 Member

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    [Jul 23, 2014]
    Oh, that clip has been of a few times. Thanks for the info, I'll try and get it sorted today.
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  9. Iain-A6
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    Iain-A6 Member

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    [Jul 23, 2014]
    Another question.....the sensor that's in the lower rad hose with a plastic clip, is that defo the temperature gauge sensor?
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  10. mrnice
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    mrnice Member

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    [Jul 23, 2014]
    I've not noticed a sensor in the bottom hose?, I can say that the sensor in a housing at the back right of the block is the coolant temp sensor which feeds the Ecu and temp guage, commonly changed to cure problems with engine not getting up to temp.
    This is correct for engine codes AWX and AVF.
    Maybe someone with more tech know-how can advise further regarding a sensor in the bottom hose?

    What year/engine code is the car btw?
    Last edited: Jul 23, 2014
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  11. Iain-A6
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    Iain-A6 Member

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    [Jul 23, 2014]
    My car is 2000, 1.9tdi the engine code is AVG. Only sensor I can see is into the top of the oil filter housing and there are various plastic houses with clips, one on the left and one on the right.


    Please help, I lifted the coolant tank and water came out straight away from the bleed hole, it must be a faulty temp sensor. It gets to 90 and then drops to 0 and does move again.

    Just need the location and Colour so I can order a new one.
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  12. Iain-A6
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    Iain-A6 Member

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    [Jul 23, 2014]
    I have found a sensor that goes into the top head coolant hose and has a plastic clip, it's black in Colour with four wires??
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  13. mrnice
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    mrnice Member

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    [Jul 23, 2014]
    Ok so first my apologies, everything I've been whittering on about relates to the later AWX engines. I have no experience of the earlier engines I'm afraid but can maybe help a little-

    The coolant bleed procedure I expect is the same anyhow but it seems the coolant temp sensor is indeed in a different place. here's a diagram of AVG from vag-cat.com. The sensor is item number 9 (near top of pic). It's attached to a housing at the back of the head.
    [​IMG]
    As far as i remember I just took the sensor along to Audi parts dept where they gave me a green version which supersedes the black one.
    I'm at the limit of my (limited) knowledge here, so I'm hoping someone with knowledge of the earlier engines can chime in.
    Btw if you'd like to score vag-cat boards parts catalogue to help you have to join the forum but it's very useful-

    VagCat boards

    best of luck
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  14. Iain-A6
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    Iain-A6 Member

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    [Jul 23, 2014]
    Fitting a new temp sensor has worked, but that diagram is wrong . I found it myself.
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