freshly assembled maybe it has an airlock in it, feel the 2 hoses near the firewall and see if both get hot - disconnect one of the hoses and get a flow thru it - try switching the 2 hoses so the flow is reversed .... might also have a defective valve [new even] restricting it, replace with a piece of copper tube until you sort things out .... the fan should push plenty of air, maybe you have the rotation backwards?
Bill
