I concur. Everything else seems to be checked out. The radiator itself may be the culprit. You've probably mentioned this before, but has the radiator been completely flushed and the coolant reservoir checked? There may be a clog or blockage caused by sludge in the system that is creating this condition.

 

I think at this point you have determined that the flow of coolant is likely the issue. If the radiator is still in good shape and you can flush it successfully, I would move on to the Heater Core. If it is clogged and restricting coolant flow, you would definitely see the symptoms you have described. I am curious if you have made sure that there are no air pockets in the system. Does the heat blow out hot consistently? As for a possible control module issue being at fault, I would think you would see other systems being affected as well. This is not a definite certainty, but keep your eye out for other weird issues that seem to make little logical sense. Also, if the control module is malfunctioning, it would throw its' own, unique ODB code. Good luck.

 

I have an '07 3.8L Pacifica. One of my fans began to wobble severely about 8 months ago, so I disconnected the harness, and have been running on 1 fan ever since. Not to contradict your suggestion or anything of the sort, but one fan should keep it cool enough if the rest of the system is functioning properly. I'm glad that you were able to resolve your issue by replacing the fan assembly, but be sure to keep your eye on the other components of the cooling system because it's possible there may be a small issue or the start of an issue with another part of your cooling system.

 

Problem finally solved. My PCM needed to be replaced. Let me take a step back and outline what happened to help people that might have a similar problem.

After changing a lot of sensors (IAT(Intake Air Temperature), ECT(Engine Coolant Temperature), fan relay and even thermostat and radiator the engine coolant temperature was still climbing high and the coolant was boiling over. I noticed that the fans were coming on and off but did NOT stay on when the coolant temperature exceeded 240F. Two additional "strange" things. Error code P0113 (for IAT sensor high) would not clear and the registered temperature and voltage at the sensor stayed constant at 66F and 5.2V. Furthermore, I never received error code P0480 (Cooling Fan Control Circuit) to alert me that something might be wrong with the fan wiring. I performed the check procedure for IAT and for Cooling Fan Control Circuit and in both cases the wiring, grounds etc checked good i.e no shorts or opens with a malfunctioning PCM remaining the ONLY issue. Since then I replaced the PCM and everything worked fine.

Thank you all, for your great help and suggestions.