If you look at the expansion tank from the driver's seat point of view, there are two tubes that run to/from the tank cap. On the left side is the radiator return hose. It runs all around the driver side of the engine compartment to the top of the radiator. On the other side is the tank overflow tube that runs toward the passenger side of the firewall and then down toward the ground. Where exactly did you notice weeping coolant? There are two coolant hoses that run underneath the intake manifold. These can leak and cause drips. There is also a nest of hoses by the thermostat housing. If those hoses leak at their connections, they can cause coolant to trickle down the side of the block. HTH