Fan overspeed?

[JHardwick]

In 150,000 miles I've never heard my fan except in a low speed condition ... ... ... ... leaving a parking lot, short little side streets etc ...



Here recently my fan has been coming on at highway speeds over mountain passes etc. I can here this thing at 70MPH with the radio blasting and a trailer in tow at 30* outside temp.



I called home with some codes and "fan overspeed" was one of them, what gives?

 

[JHardwick]

nobody ??

 

[formula]

Fan clutch wasted perhaps? With the engine off and cold try to turn the fan by hand. It should turn with only a little resistance.



What does your engine temp gauge read when this happens?



Sean

 

[JHardwick]

I can spin the fan freely by hand. The temperature does climb a tad to just above 200* when the fan comes on, but it never did it before.



Maybe adding the "Prestone - add to any system" coolant has me starting to clog up, making temps condusive to the fan running at highway speeds and giving a "fan overspeed" condition. ??

 

[MCummings]

If you are running to much anti-freeze, and not enough water, the truck will be more prone to higher water temps.





Merrick

 

[JHardwick]

I dumped in the 50/50 premixed stuff, about 2 quarts worth, brought me back to full.

 

[Bob4x4]

I dumped in the 50/50 premixed stuff, about 2 quarts worth, brought me back to full.

Just curious why did it need the 2 quarts?



Bob

 

[betterthanstock]

In 150,000 miles I've never heard my fan except in a low speed condition ... ... ... ... leaving a parking lot, short little side streets etc ...



Here recently my fan has been coming on at highway speeds over mountain passes etc. I can here this thing at 70MPH with the radio blasting and a trailer in tow at 30* outside temp.



I called home with some codes and "fan overspeed" was one of them, what gives?

Maybe time to replace thermostat. Also, temp sensors may need checking out. Air pockets in coolant next to thermostat cause it to read too low. Bleed coolant in head? Frayed wiring insulation rubbing against radiator (early 2003 problem) or A/c compressor under engine can get the fan running when it should not.

 

[JHardwick]

Just curious why did it need the 2 quarts?



Bob

Dunno, LOL.

 

[JHardwick]

Maybe time to replace thermostat. Also, temp sensors may need checking out. Air pockets in coolant next to thermostat cause it to read too low. Bleed coolant in head? Frayed wiring insulation rubbing against radiator (early 2003 problem) or A/c compressor under engine can get the fan running when it should not.

I don't think the AC was ever quite right, but I don't think it is a coolant problem. Maybe a thermostat, but it only does it on long pulls up mountain passes. I thought maybe the belt, since it has 150,000 miles on it, wasn't turning the water pump hard enough, but that usually shows up in the alternator first. I can'r really say I see a "spike" in water temp, but it does go to just past 200 when the fan starts to run.



Wiring is fine.



Doesn't a steam pocket read hotter, not cooler?