Any ideas what this could be?

[pmpski_1]

The engine starts getting really hot - seems like it's not getting the coolant it needs.

There is a strange substance in the radiator and the coolant is an off color. Bought a new thermostat and tested it before installing, so I know it's working.A buddy says it's got to be the head gasket so I started tearing it down. I haven't got the heads off yet, but I came across this stuff after taking the manifold off.

Any ideas about what this could be? It's soft like butter and feels slightly oily, but it's solid. There's a slight bit of it on the inside of the hoses too, but it's just a light coating, not built up like this. I've never seen oil from a blown head gasket, so if it's that obvious, well, I can chalk it up to lack of experience.