If it's a 3.5L then it's on the passenger side of the engine. Follow the lower radiator hose (the larger diameter hose it's also on the passenger side) and it will connect to the thermostat housing. The housing has two hoses, the previously mentioned hose from the bottom of the radiator and another smaller diameter hose from (what I assume to be) an oil cooler. The housing will have 3 bolts (10mm) that you will have to remove, the rear one is difficult.
