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  1. #1

    Default aqad 40 coolant loss.

    I am jim from greece and I have an
    aqad40. I restored it, the exchanger was
    fully clogged and overheated to the
    previous owner.I resurfaced the head and
    there is a small crack between the valves
    in the 5th cylinder(only visible if you
    use a hand focus), but the pressure test
    showed no leaking and I reinstalled the
    head. Injectors are new, heat exchanger is
    cleaned (both head and exchanger works
    carried out from special personnel and i
    am also mechanic).Engine runs as new and
    the cooling system works perfect but I lose
    some coolant, about a liter per 10 hours.I
    can't find any external leaking and also I
    try to find if it's loosing coolant when
    engine is resting.My worse thought is what
    if there is leaking in the cylinder under
    several conditions and how much could be
    that loss? a liter per 10 hours seems too
    much for me.What is your opinion? Regards,


    Jim.

  2. #2
    Join Date
    Mar 2009
    Location
    Brusly, LA
    Posts
    171

    Default Re: aqad 40 coolant loss.

    Is coolant getting into your oil? Have you tried to pressure test the cooling system? After sitting a few days, does the engine start easily? Try Barr's stop leak. I have had success with it in the past.

  3. #3

    Default Re: aqad 40 coolant loss.

    Quote Originally Posted by jimgreece View Post
    I am jim from greece and I have an
    aqad40. I restored it, the exchanger was
    fully clogged and overheated to the
    previous owner.I resurfaced the head and
    there is a small crack between the valves
    in the 5th cylinder(only visible if you
    use a hand focus), but the pressure test
    showed no leaking and I reinstalled the
    head. Injectors are new, heat exchanger is
    cleaned (both head and exchanger works
    carried out from special personnel and i
    am also mechanic).Engine runs as new and
    the cooling system works perfect but I lose
    some coolant, about a liter per 10 hours.I
    can't find any external leaking and also I
    try to find if it's loosing coolant when
    engine is resting.My worse thought is what
    if there is leaking in the cylinder under
    several conditions and how much could be
    that loss? a liter per 10 hours seems too
    much for me.What is your opinion? Regards,


    Jim.
    Hi there

    This is an old thread but I have exactly the same issue with my AQD40A Volvo Penta and I lose some coolant as well. About a liter per 10 hors as well. The oil does not show any sign of being contaminated with water and I can't find any substantial external leak although the expansion tank cap is leaking a bit. I can open the expansion cap when running at 2800RPM and I can't notice and blowby pressure from the expansion tank.

    Also, I can't see and white smoke indicating coolant being burned in cylinder due to cracked head / blown head gasket but as the exhaust gases are directed in the water I'not sure if I could see any white smoke in anyways.

    Any other fellows with similar issues? I'm a bit puzzled? However, I'm not tempted to remove the cylinder head as the engine is running perfect and maintains steady temperature of 75-78 celsius degrees depending on the rpm. The oil pressure is also ok.

    Any thoughts?

    -Artto

  4. #4
    Join Date
    Jun 2008
    Location
    Posts
    544

    Default Re: aqad 40 coolant loss.

    If the missing coolant isn't in the bilge or oil then it must be going out the exhaust. It can't go anywhere else. Could you have a pinhole in the aftercooler? Also, is the turbo cooled by coolant or seawater? If the turbo is cooled by coolant a cracked turbo housing may give coolant loss. Have had this on a different type of marine diesel.

  5. #5

    Default Re: aqad 40 coolant loss.

    Quote Originally Posted by aliboy View Post
    If the missing coolant isn't in the bilge or oil then it must be going out the exhaust. It can't go anywhere else. Could you have a pinhole in the aftercooler? Also, is the turbo cooled by coolant or seawater? If the turbo is cooled by coolant a cracked turbo housing may give coolant loss. Have had this on a different type of marine diesel.
    Hi Aliboy,

    Thanks for your reply,
    Mine is without intercooler. (AQD40A as oppositeto AQAD40A)

    The turbo housing could be culprit to the matter as it's freshwater cooled, thanks! I need to check that

    btw where did the turbo housing cracked in your case?

  6. #6
    Join Date
    Jun 2008
    Location
    Posts
    544

    Default Re: aqad 40 coolant loss.

    I have seen this a couple of times but not on a AQD. Between the exhaust side and the coolant side so you need to look at it from the exhaust side to find it usually. You may also be able to pressure test the coolant side by making up an adapter plate?

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