Fan clutch & altitude

[02Hank]

I recently replaced my fan clutch in my 02 1500 and saw a slight improvement in it not engaging. I was living at the time at 5300 ft. in the mountains in Mexico. I recently moved to Texas and on my way went up to 7-8000 ft which is most of the drive from Mexico City to just south of the Texas/Mexico border. The fan clutch was engaged the whole way until I came down in elevation a few hours before the border. It stayed off and occasionally would turn on while coasting downhill. Now in Dallas at about 400 ft and hardly anything, but moving early next year to Colorado Springs (7-8000 ft). Could this be a bad fan clutch? Are there alternatives to the standard fan clutch for high altitude areas? I am sure the altitude effects it’s performance...

 

[Nick_rp]

Fan clutch works off ambient temp meaning any change in outside temperature will affect how often it cycles. If you feel your new clutch is bad or failing already its real easy to test it.

Truck off, open the hood, take your hand and give the fan a good hard spin. If it spins freely with minimal resistance, its good to go. If its hard to spin, its bad

 

[ViolentMouse]

Like Nick said, if you look at the front of your fan clutch you will see a small coiled spring. That is the thermostat for the fan clutch, as air moves over the radiator (and optional coolers) it draws heat out of them and that heated air runs over that thermostat. Your clutch is filled with a fluid and that thermostat controls the movement of that fluid. More heat = more fan clutch lockup, less heat = less lock up

As you go up in altitude the air is less dense and less capable of heat transfer, so it would make sense that the clutch stayed on longer to draw more air over the coolers as the thinner air would take longer to draw heat out.

as far as the spin test.... there is a caveat. If the truck is hot and you have just driven it, expect that the clutch would be in the "engaged" or tight mode and would be hard to turn.... so if it spun freely when hot that would mean it is NOT good. if the truck was cool and it did not turn freely the clutch would be no good.

after 40mph the fan does nothing as it draws no more air than what is already flowing through the cooling fins of your radiator and optional coolers, but a fan clutch setup doesn't care about speed, only temp.

If you are hearing your fan cycling on and off, usually it is working, but if you are hearing it a lot, I would be concerned with why....maybe you are running hot?

Your truck is designed to operate around 210 degree F. from the factory you have a 195 degree F thermostat installed, and for the most part it's a good solid number, but those of us living near or in a desert usually swap in a 185 so we have a winning chance of moving coolant before overheating does damage.

Also I make it a habit to drill at least a 1/8th inch hole in my thermostats to allow the system to bleed air when cold filling with coolant. (prevents trapping air in the intake)

 

[Nick_rp]

Like Nick said, if you look at the front of your fan clutch you will see a small coiled spring. That is the thermostat for the fan clutch, as air moves over the radiator (and optional coolers) it draws heat out of them and that heated air runs over that thermostat. Your clutch is filled with a fluid and that thermostat controls the movement of that fluid. More heat = more fan clutch lockup, less heat = less lock up

As you go up in altitude the air is less dense and less capable of heat transfer, so it would make sense that the clutch stayed on longer to draw more air over the coolers as the thinner air would take longer to draw heat out.

as far as the spin test.... there is a caveat. If the truck is hot and you have just driven it, expect that the clutch would be in the "engaged" or tight mode and would be hard to turn.... so if it spun freely when hot that would mean it is NOT good. if the truck was cool and it did not turn freely the clutch would be no good.

after 40mph the fan does nothing as it draws no more air than what is already flowing through the cooling fins of your radiator and optional coolers, but a fan clutch setup doesn't care about speed, only temp.

If you are hearing your fan cycling on and off, usually it is working, but if you are hearing it a lot, I would be concerned with why....maybe you are running hot?

Your truck is designed to operate around 210 degree F. from the factory you have a 195 degree F thermostat installed, and for the most part it's a good solid number, but those of us living near or in a desert usually swap in a 185 so we have a winning chance of moving coolant before overheating does damage.

Also I make it a habit to drill at least a 1/8th inch hole in my thermostats to allow the system to bleed air when cold filling with coolant. (prevents trapping air in the intake)

Im so used to doing rather than explaining that i forget to mention certain things. Like clutch resistance on a hot vs cold engine. Nice write up

 

[grpht03ram]

I have a few thoughts:

1. Did you buy an OEM fan clutch? The only aftermarket clutches available are heavy duty and severe duty clutches which engage more often (at lower temperatures) and spin faster (more noise) than OEM. Nothing will be quieter than the OEM fan clutch

2. You were driving up a grade. the engine created more heat = fan on more often

The combination of the steep grade and a heavy duty fan clutch created a condition where you probably heard way more fan noise than you normally do

I recently replaced my OEM fan clutch with an aftermarket severe duty clutch and its way more obvious when the fan is engaged.

 

[02Hank]

The replacement clutch was not OEM so maybe why it’s engaging more often. I am pretty sure the altitude has to do with it engaging constantly in addition to it not being OEM. The body of the clutch looks a lot beefier than the original as well. And when I said altitude I meant normal driving conditions at high altitude (flat) and not driving up inclines. The clutch actually disengages when I go up inclines. It really has nothing to do with temperature at this point. The truck is not hot (just below middle on C side) and has a 185* thermostat. Now that I’m at 500 ft it barely engages, only starting off from a complete stop. I’ll find an OEM to replace it and problem fixed hopefully. But had no idea altitude had an effect on them.

 

[02Hank]

[QUOTE="Truck off, open the hood, take your hand and give the fan a good hard spin. If it spins freely with minimal resistance, its good to go. If its hard to spin, its bad[/QUOTE]

It spins but doesn’t freely spin. In other words I can move it without effort but it doesn’t spin after on its own. It’s not loose at all. Does that mean it’s bad?

 

[grpht03ram]