[clc900]

Had the day off so I took the manifolds off to inspect. The manifold on the warped hose side checked out good. Needs cleaning up a bit before I put it back on but it looked good. Since I had one side off I decided to take the other side off. Inside looked good. Upon further inspection it looks like I have a hole in my manifold!!! ***!

Here is pic.

How do I fix it. What caused it? Anything else I should check while I have the manifolds off?