Overheating Issue

[04 MT]

Hi guys, today I was driving the 550 up a mountain pass probably around 30,000 gross. I noticed for the first time ever that the temperature gauge was climbing up towards the red mark. I was holdin the EGT's at 1250 like I always do when pulling this pass. Just about the time the needle hit the red mark, I heard the fan come on and the temps dropped down to normal but then the fan shut down and the temps climbed and the process repeated.

I got to the top where there is a pull over spot thinking maybe there was something blocking the radiator, it was clear. This truck has never once had the temp gauge go much over half way and I have pulled heavier loads at higher ambiant temps then what today was.

So I'm thinking maybe it's the fan clutch? The coolant level was fine, oil level was fine, and the thermostat doesn't seem to be sticking. The temps were fine while going on the flats at 65 mph. If anyone has had similar issues to mine could you please post what the solution was. Thanks guys!

 

[Pocket]

In almost every case like this it's the water pump cavitating and dying.

 

[04 MT]

I picked up a motorcraft thermostat today and am gonna change it out tomorrow. I felt the fan clutch and everything seemed normal there, no leaks, no wobble, and there was resistance when trying to spin it by hand. After driving the truck today I think that the thermostat is stuck part way open. I'll post tomorrow what I find.

 

[04 MT]

Ok, I replaced the thermostat. The old one was not stuck open but did feel like it may not open all the way. I didn't pull my trailer today but I still weighed in the neighbor hood of 15,000 lbs. I went up a 6% grade thats about 3 miles long and the temp gauge never went higher then halfway up.

Now for the weird part...Before I would have to kick the cruise control off at even the slighest hint of a hill because the EGT's would quickly climb past 1250*. Today I was able to leave the cruise on and EGT's stayed at 1200* or less even on the hill. Also before the thermostat change, I'd get a check engine light with a code of "excessive ICP" whenever I was in 6th gear and the engine would work a little, today the check engine light never came on.

So would a thermostat change affect EGT's and ICP pressure? I just lived with the ICP thing before...as in 40,000+ miles. I know the factory temp gauge probably sucks but I'm thinking that my thermostat has been screwed up for quite some time.