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A4 Overheating

Discussion in 'A4/S4 forum(B5 Chassis)' started by holez, Sep 12, 2011.

  1. holez
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    holez New Member

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    [Sep 12, 2011]
    Hello All

    I have a 1998 A4 and I took it away over the weekend.
    I noticed the temperature went above normal levels while driving on the motorway so I pulled over. When I pulled over and the car was at idle the temperature came back down again which I thought was strange.
    As I had to get the car home I checked the water and topped it up and continued driving. Again when on the motorway the temp went up.
    I continued like this driving at 50mph where the temperature would stay below dangerous levels but still above normal operating temp.
    I had to pull over several times to top up the water.....which was going down but I couldnt see it leaking anywhere.
    I also notice that the fan was working but the second thermo fan was not.
    What is the second thermo fan for and why would the car be loosing water but no leaks seen in the engine bay?
    Thanks very much. ​
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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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    [Sep 12, 2011]
    About the only explanation for losing water with no leaks is a headgasket failure. That can also cause overheating, or conversely the overheating can cause head gasket failure.

    It could also just be a leak, coupled with a faulty water pump.

    How far down was the coolant level getting? I found on my old car it would creep down to minimum and then stay there. It was clearly leaking, but i never found it and just left it at minimum.

    I think your cheapest first step is to whip the water pump out and see if its still in one piece.

    On the fans, the big one is driven by the engine, and will run all the time. The smaller one serves two purposes, one to help cool the AC condenser in traffic, and to help the viscous fan out should the coolant temperature exceed 100c.
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  4. holez
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    holez New Member

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    [Sep 13, 2011]
    I thought it may be a headgasket too but when I checked the oil it was perfectly clean. If it was leaking through the headgasket, especially so much of it, it would get into the sump no?

    The coolant was getting pretty low. It took about a 1.5L to fill to the top again.

    I really hope its not the water pump or the head gasket. I think both would be expensive repairs on a car that really isnt worth that much anymore.
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  5. S4_dan
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    S4_dan Fire up the Quattro!

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    [Sep 13, 2011]
    Blown HG's won't always mix water with the oil. I've had one blow on a Saab C900 Turbo recently and that wasn't mixing oil/water but was putting water through the turbo unit into the exhaust.

    IF your a member of the RAC etc, call them out when your parked up down the road. They have a test 'thingy' that they place into the headertank with engine running. It will change colour 90% of the time if the HG has failed.

    Or you could do a compression test on each cylinder to see what values each cylinder is holding.

    Can't you see when the engine is warm that the return water pipe in the headertank is flowing water?
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  6. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Sep 13, 2011]
    yeh they can blow between the coolant jacket and the cylinder itself, so the water just gets burnt off and can result in steam from the tailpipe if its leaking badly enough.

    If its a 1.8 the water pump is external, and pretty easy to get at and remove, hence my suggestion that it would be a useful first step to diagnosing it.
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  7. B5NUT
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    B5NUT Well-Known Member VCDS Map User

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    [Sep 13, 2011]
    What engine do you have?
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  8. holez
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    holez New Member

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    [Sep 13, 2011]
    Thanks for your help guys.

    I have a good mechanic down the road so will take it to him on Saturday.

    Will let you know the result.

    Whatever it turns out to be I hope its not too expensive!
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  9. holez
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    holez New Member

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    [Sep 13, 2011]
    1.8 Petrol
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  10. holez
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    holez New Member

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    [Sep 13, 2011]
    Hi Again

    I have been doing some more research and it could also be the heater core.

    Does anyone know how I could test this?

    Also Im guessing its a difficult thing to replace, any idea on cost?

    Cheers
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  11. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Sep 13, 2011]
    If the heater was losing as much water as your suggesting you'd probably have steam belching from the vents and misted up windows...
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  12. holez
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    holez New Member

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    [Sep 19, 2011]
    Hello again

    Ok so on the weekend I managed to get to the thermostat and removed it to see if that was actually the problem.

    I ran the car and it still overheats.

    I had a friend rev the car at 3000rmp when it was warm and there seemed to be a little condensation coming out of the exhaust. If the head gasket was stuffed, but no water going into the engine that I could see via the dipstick, how much steam or water would be coming out of the exhaust.

    Thanks again
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  13. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Sep 19, 2011]
    Check the water pump.

    The impeller is made from plastic and can crack and come detached from the shaft.
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  14. holez
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    holez New Member

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    [Sep 26, 2011]
    Hi guys

    So for anyone that is interested I took the car to a mechanic on Saturday and he has just rang to say its the water pump.

    I really dont get this as there is clearly water going somewhere and nothing is leaking out of the water pump or anywhere in the engine bay so Im still really unsure.

    Guess we will see.

    Cheers
    #13

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