Volvo Penta

I have a motor Volvo Penta AQD 41A in my boat, and now I have a problem that
I don't get to identify. - The motor usually works, meantime after some
hours of use, it expels the whole lubricating oil through the breath filter.
I made the test of compression emission opening the cover where the oil is
put, and I didn't notice any compression emission.
I would like somebody to guide myself to I respect, because several
mechanics that I consulted myself didn't give a satisfactory answer.
The apparent causes would be rest in the pistons, but that is not true
because the motor is not with the level of the low oil.
Thanks
Fernando

 

I had this some years ago and it was due to worn bores/piston rings. When
the engine is 'cold' say on a short run the viscosity of the oil in the sump
was high enough to resist the pressure leaking past the pistons and was not
blown out of the crankcase breather. If used on a long run then the oil
would get blown out and this would happen over a small rise in oil
temperature. The apparent performance of the engine did not seem to be
affected. It worth noting that small rises in temp (20C)can reduce the
viscosity of oil by half
The cure was rebore and new pistons.
It would be worth checking that if you have bought this engine second hand,
that all the pistons have all their rings, as I have seen engines with the
rings missing altogether.

Hope this helps.....ttfn......Alistair