My truck has no mods and I'm not towing, 180k miles. It used to run 200-210 all the time, now it seems to fluctuate 180~210, but on a trip with some hills leaving Phoenix, it ran up to 230 and started jumping higher then lower... I downshifted to keep the RPMs up, but hills are definitely affecting the temp (in a scary way). Also noticed engine was not responsive, power was low. Any ideas fellas? I had a CEL later in the trip, haven't checked it yet.

Thanks

 

Replace thermostat

 

Usually, in the interest of keeping my vehicles reliable, I will throw in a new thermostat when I have the cooling system apart, like to replace the coolant, as it isn't a lifetime part. If yours is original, it's probably worth replacing it, hopefully it improves the condition. I would also take the hose and clean all the grime from the fins of the radiator.

 

And be sure that's the garden hose you use, and not the high pressure air hose...High pressure air can bend the fins of the radiator and block air flow...Don't ask how I know......Ben

 

Picked up a thermostat today. On my way home, the temps dropped well below 170 when going downhill, looks like it's probably stuck partially open. I will update when I get it switched out. Thanks for the advice!!!

Dan

 

Check the code for the CEL you got and let us know! Sometimes, the fan clutch can act up as well. Thermostat is good to change just in case as said all ready.