Coolant dripping from overflow hose on heat exchanger Volvo MD2030

[Harveyhall]

The cooling system on the MD2030 has an return from the TOP of the cap of the heat exchanger to the expansion tank an another line back to the TOP of the cap. There is also a small overflow hose as seen in many car radiators. Websites linked below show overflow hose and hoses to expansion tanks.

The expansion tank system is working but why would it then still drip a small amount coolant out the overflow hose?

This one shows overflow hose on cap.
http://www.marinepartseurope.com/en/volvo-penta-quick-find.aspx?Catalog=7740690&Category=26&View=4161

This one shows the expansion tank from top of heat exchanger.
http://www.marinepartseurope.com/en/volvo-penta-quick-find.aspx?Catalog=7740690&Category=26&View=573

Thoughts?

[JEN-et-ROSS]

I had this problem on a Mitsubishi L200 pick-up a few years back. I'm sorry to say that the head gasket had blown. .!! It just got worse until I had to do something about it.
I sincerely hope in your case it's not the gasket. .......Bill

[Harveyhall]

Ouch, hope it is not a loon head gasket either.  Thanks.....

[Jake]

Yes, Volvo chose a very unique way to plumb the overflow coolant tank.  I don't really understand it, but haven't taken the time to examine the cap on the top of the heat exchanger.  A typical car would have only one hose going to the bottom of the expansion tank and no hose that would flow onto the ground.

My radiator cap is also slightly loose and I've noticed a bit of coolant around the neck.  I may try buying a new cap which will fit tighter, or perhaps a new gasket.  Either way, the engine should never let coolant run into the bilge.  It should return to the expansion tank as the engine heats up.

Jake

[Lyra]

This does seem to indicate that you have some kind of over pressure in the heat exchanger.
It seems to me that the expansion tank and this overflow port are independent of each other and the fact that expansion works OK does not mean that this port will not function as well.
Expansion tank is connected to the top of the cap and has direct connection to the fluid which has an open path to the tank and back.
The "overflow" port is located above the cap sealing ring and generally has no contact with the fluid. But if during operation the pressure rises above a certain level than the gasket ring is pushed up a bit and provides a path to the fluid out.
Maybe it is not overpressure but simply a damaged seal ring, or check the mating surface on the exchanger for some kind of debris.