replace the water pump i think it will help you and solve your problem.

 

We little sit for a bit to cool while I checked for leaks and to make sure the water pump belt was ok. Everything looked good and after a short bit was able to slowly get the coolant cap off, there was coolant in the tank as well.

 

WATER PUMP!!!! Change it out, replace thermostat/Radiator Cap/Flush coolant and replace with Fresh Dex-Cool and Distilled water/add coolant system sealant tabs-12/and your all done no more flexing needle. Also keep your nose on the from of the car for coolant odor. Radiator may be going out.

 

4.6 liter had issues with the head bolts pulling the threads out of the bolt holes... happens gradually over time... symptoms start as you describe in your original post progressing to complete overheating... there are a number of repair kits available the best ones require redrilling taping and installing studs in the place of the head bolts... plan on spending $2500-$4000 for a reliable fix... usually happens between 85000 and 120000 miles. Mine happened at 86000... I sold mine.