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Discussion Starter · #1 ·
I have two 2008 Impala's, both with the 3.9.
One was taken much better care since day one, the other I bought after it was abused for 12 years. While most of the issues have been corrected, I am chasing one outstanding problem. The 08 LTZ runs hotter than the other 08 LT. I have replaced the water-pump, the thermostat, and the coolant. I also replaced the radiator cooling fan with a cheap Chinese ultra-power replacement that I am not 100% sure is working correctly. The vehicle runs around 205F driving 50 mph. In stop and go traffic the car however between 225-229F. The temperature gauge is not indicating an overheat and the car not actually overheated. It just runs hot in a range that I don't consider normal. The 08 on the other hand runs 195F at 50 mph, and 207F in traffic.

Two things I'm thinking -
Is the cooling fan activating on schedule? If you turn the A/C on the passenger side fan is not always on. It will turn on, but it is not always on. Does anyone have the triggers that activate both fans and their condition to do so?
Could the radiator not be working right? I don't believe there is a blockage in it, and I bled the coolant system when I changed fluids using AC Delco coolant. But could this radiator just not be dissipating heat like it is supposed to?

I ordered a new coolant cap, FWIW there is no indications that has been any leaks around the cap and there is no coolant leaks in the system.
 

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Could be a simple gauge being out whack! What happens when you turn on the heater does it drop the temp? Also have you tried a thread in temp gauge to see if the temp on the dash is reading correctly? Do you have a inferred temp gun? If so try running both cars the same distance and use it in the same place and the exact distance also.
 

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Discussion Starter · #3 ·
Using the digital read off the blue driver OBDII port, probably wouldn’t have noticed anything wrong had I not been troubleshooting a rough idle problem. The gauge is definitely functioning properly.
 

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Sorry not specific enough! The radiator inlet to outlet or top to bottom. If the numbers posted are what was mentioned, the radiator itself is doing it's job.
 

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Are all of the air deflectors / air dams in place? I had a '03 Malibu that had a missing air dam due to road debris. It had cooling issues until I replaced the air dam.
 

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Discussion Starter · #10 ·
The problem was two broken wires in the car's harness, the electrical current was jumping from one wire to the other giving indications of electricity being supplied but the fan not working because it was not enough current to operate the fan. A great mechanic fixed for $80!
 
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