If it was #3 and #4 that had coolant in them I'd be willing to bet the coolant nipple on the back of the intake that the hose from the heater core connects to has a crack in it somewhere. That's where mine started leaking from and it filled #3 and #4 with coolant.

Good thing that the intake manifold will be covered. You could see if valve cover gaskets would be covered, too. biggrin