Cub cooling system

[nat]

What is my cub telling me? When I remove theradiator cap and run it at an idle I see it turning the water over as I think it should, but if raised to mid throtle it has bubbles in the neck and if goosing the throtle wide open and then to and idle and back it will spew water out till the water level is below site.Is it telling me I have a blown gasket/ crack? It has always lost some water in use such as plowing the garden or scraping my drive which is pretty long and wide. Can someone tell me what it is saying ? Thanks, Nat

[Puffie40]

Bubbles does mean combustion gasses are getting into the water, usually from a bad head gasket. A crack will be harder to detect until you have the head off.

While you have the head off, check both the head and block surfaces for flatness, as uneven surfaces will also cause the head gasket to fail.

[nat]

I was sort of afraid that was the message it was sending. I don't need it right now so it would be a good time to do the repairs. Thanks, Nat

[Eugene]

Before you take any drastic actions, flush the entire cooling system. Use the search function, there are several topics on the subject, including a recent one.

Crud and scale build up in thermosyphon cooling systems. Crud and scale cause hot spots on cylinder walls.