I assume the cooling fan on these trucks is still a mechanical device that's activated by temp? With all the computer-controlled crap on these trucks I can never take it for granted!

I've noticed several times that when driving away on a mostly-cold engine (first drive of the day), I can clearly hear that the fan is engaged and the temp gauge is barely on the first notch at C. Does this mean the clutch is failing? I had one die in my old GMC and it failed in the open position, meaning overheating. I replaced it with a custom E-fan setup and it was very nice afterwards. My 350 TBI extended cab 4x4 got consistent 15 mpg in town where my current truck is stuck at 9 and only 11 on the highway.

I plan to do an E-fan on this truck too but wanted to do it on my own schedule. If my fan clutch has siezed I may be doing it sooner than I thought. Any suggestions on testing its effectiveness?

 

My 06 with 12,500 on the clock has the clutch fan kick in almost every time I drive off from a cold start.

 

Your fan clutch is a fluid filled unit that's thermostatically controlled. When you start your truck/car, it doesn't spin at full speed, releasing to save hp and ultimately fuel savings.

As the vehicle warms up and warmer air comes in through the radiator, the thermostat in the unit starts to kick in and lock the fan up harder.

The fan can fail in 2 ways...

1.) The clutch mechanism fails and the fan spins freely most of the time, causing overheating as won't draw enough air through the radiator at low speeds. (High speeds the radiator air becomes cooler and the fan clutch releases a little)

2.) Internal mechanical failure and the fan locks up permanantly and the vehicle over-cools on cooler mornings.

 

What you are hearing/feeling on a cold engine is the transmission. It tells you this in the Manual. It does that untill the fluid in the transmission is flowing better or warmed up a little. Something like that anyway.

 

I certainly hope my transmission doesn't sound like a fully-engaged cooling fan!

I'll check out the fan clutch in the next few days. I don't have a problem with over-cooling; that is, the temps reach the normal resting spot that they always do. However, if the fan is engaged when it shouldn't be it's costing me mileage.

 

I did the e-fan thing, a Flex-a-Lite 180 Extreme. Has it's own thermostat, I have it set at 170*, and I have a Jet 180* Thermostat. I don't know how many ponies it freed up, but my "butt dyno" can tell the difference, and for some reason the gas pedal feels like it's light, or has less reistance, also seems to coast farther when coming to a stop, so I'm letting off the gas sooner. As I have only gone back & forth to work and take the same route as always, it's safe to say I'm seeing about a 1.2 mpg increase to boot.