Volvo Penta TAMD71B Coolant Leak

Our boat has a Volvo Penta TAMD71B. The other day, we checked the coolant level in the morning (normal level) and ran all day. The next day, I went to check the expansion tank and it was bone dry. The fluid was in the bilge. We filled the expansion tank back up, and ran the engine at idle and there were no leaks. The boat runs at 150 deg. when at idle cold and gets up to 180 deg. when operated (normally and now). At 180 deg. coolant starts rushing out of the expansion tank. Puts out about a gallon or more before stopping. Our mechanic said over the phone that it was the radiator cap. I replaced it this morning, and the same thing happens. He said that it was just pushing off excess coolant (overfill) and that everything is fine. Not sure why he didn´t say that yesterday.

But, this doesn´t explain the original problem of the tank being bone dry.

Anyone have some suggestions? Is a blown head gasket on the table?

Thanks in advance for any feedback,

Rip

I would look for a cracked manifold before head gasket. Did you pressure test cooling system?

Hi did you solve the problem, and if so what was was it as I seem to have the same thing.It has been said that it may be the manifold to turbo gasket.

I have 71A and both my tanks are dry, i.e. you cannot see the coolant or feel it, and both engines run fine. If I top them up it just comes out back to a lower level.