After numerous flushes, new thermostat(185 degrees), and new heavy duty radiator my 5.2L continues to heat-up to over 225+ degrees when the outside temperature is 85+ degrees.  The dealer says its running find, but after having the vehicle for almost 8 years it has only begun to do this over the last two summers. The vehicle also runs rougher when the temperature is over 210 degrees.  The activities that raise the temperature gauge to 210+ the fastest is driving up hill, idling in traffic, or parked idling on a incline.  The last one may be the best clue, but not sure to what...  If you got any ideas, I would surely appreciate the input...  

jwahl:
After numerous flushes, new thermostat(185 degrees), and new heavy duty radiator my 5.2L continues to heat-up to over 225+ degrees when the outside temperature is 85+ degrees.  The dealer says its running find, but after having the vehicle for almost 8 years it has only begun to do this over the last two summers. The vehicle also runs rougher when the temperature is over 210 degrees.  The activities that raise the temperature gauge to 210+ the fastest is driving up hill, idling in traffic, or parked idling on a incline.  The last one may be the best clue, but not sure to what...  If you got any ideas, I would surely appreciate the input...

If the water pump impeller becomes loose on the shaft it’ll revolve at a slower speed than normal. also if the water hoses collapse inside they’ll obviously restrict the flow rate, even the heater hose if it’s part of the normal cooling system. The worst case I’ve had was a cylinder block that had 75mm of sand in the water jacket that hadn’t been cleaned out after the casting process which i had to remove through the core plug holes. Have you taken a plug cut to see if the ECU isn’t leaning off the mixture either because of a fault in itself or a sensor connected to it?  

even just a smill hole could cause it to over heat slightly, have you had it pressure tested? not leaking, but sucking air in your system. Puting in a lower themostat will only cause you to get worse gas mileage, your computer calls for a 195, i know its not much and it was worth the try, but your computer will always think it is in warm-up still and dump in more gas than called for. also you could try a new clutch for your fan, or check your shroud for a crack, it would have to be a big one though. try cleaning all the bugs off your ac condensor,  

You did not mention if you are having to add coolant or not. If you are, have the cooling system pressure tested, any shop, dealer or radiator shop can do this. If it has a visible leak replace the offending part. If the system is pressure tested with no visible leak the culprit is most likely a blown head gasket. If you are not losing coolant the above posts are good places to start. Also you say you replaced the radiator, and it seems to overheat parked on an incline. This suggests air trapped in the cooling system and needs to be removed. Make sure your overflow coolant tank hoses are hooked up and not dryrotted (sucking air) and the tank is filled to the correct level. As the coolant cycles it should remove any air trapped in the system.  

Yes, began leaking coolant shortly after I posted my problem.  Worn water pump bearing.  Replaced water pump that looked good otherwise.  I am running a little cooler, but still heat up to 210-215 when outside temperature gets above 85. I will check hoses.  No longer loosing coolent..

Thanks...  

Thanks for your comments.  I started leaking fluid shortly after I posted this message.  Replaced water pump that had a worn bears. It is running a little cooler (210-215) when temperature is above 85.  Gauged check and it is accurate. I will check the ECU next.  

Thanks for your comments.  I believe you are right...  I started leaking fluid shortly after my post.  Worn water pump replaced that resulted in it running a little cooler.  But still running between 210-215 when temperature is above 85.  Guage checked for accurancy, and not leaking fluid anymore.  I will go back to a 195 thermostat...  

sounds like its back to par. that temp is ok for ideling with ac, as you drive down the road, is it about 200?