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aqad 40 coolant loss.

jimgreece

New member
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.
 
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.
 
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
 
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.
 
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?
 
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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