Need to unplug/open line between exhaust manifold and coolant overflow tank. Overflow tank connects to exhaust manifold by an elbow fitting on top of the manifold. After entering the manifold the line does an immediate 90% turn and travels along the top of the manifold and terminates at the edge of the fill opening (radiator cap type). This tube seems to be pinched shut (however it could be plugged). How do I open up this tube? I've tried a stiff wire with no luck. Does this tube need to terminate/open at the fill opening? Could I pull off the elbow fitting an drill an opening thru the tube straight down?