Coolant definitely runs through the manifold. That's where the thermostat sits.
It would have to be a pretty round about path to get to the chambers, but I imagine its possible. Never seen it, but possible.
No idea how to test your intake gaskets either. Afraid I won't be too much help here, but the other guys will be, I'm sure.
Try to get a compression test done soon. That's the beet check for what you're dealing with.