The first thing that comes to mind is the head gasket test. Did you use a glass cylinder with two chambers partially-filled with a special dark blue liquid? If so, that liquid is rendered useless if it freezes or if it gets contaminated with antifreeze. Once either of those occurs, it will never change to bright yellow. In fact, this is why the auto parts stores that borrow tools will have this tester but they make each customer buy their own bottle of fluid.
Water dripping from the muffler's drain hole or the tail pipe is a sign the exhaust system is working properly. White smoke is not. Regardless, it is very uncommon to have a leaking head gasket if you don't also have a gradual loss of coolant.
When the overheating occurs, feel the upper radiator hose. It should be too hot to hold onto for very long. If it's just warm, or cold, the coolant isn't circulating. First, look on the thermostat housing for a bleeder screw to let the air out. Air will collect under the thermostat when the system is being refilled, and that will prevent it from opening. Thermostats have to be hit with hot liquid to open. Hot air won't do it. If there's no bleeder screw, look for a sensor or threaded plug that can be removed while the cooling system is being filled. If you remove a sensor, leave the ignition switch off when it's unplugged to avoid setting a false diagnostic fault code.
If the upper radiator hose is hot, I know this sounds stupid, but check that the radiator fan is blowing the right way. If the wires are reversed, it will blow air forward against normal flow when driving. That is caused by switching the wires when a fan is replaced.
Also look for a butterfly collection in front of the AC condenser. That will block air flow through the radiator.
There's one more thing I've seen happen that can cause overheating after a new radiator was installed. The old one had badly-corroded cooling fins so the radiator couldn't give up its heat. The new one came with protective plastic caps on the tubes to keep debris out. Those caps got painted when the radiator was painted, and the mechanic didn't see them or remove them during the installation. The solution to the original problem was a new radiator, but the apparent problem was still there due to those caps.
Wednesday, March 4th, 2015 AT 3:11 PM