Fan Clutch
 

Yesterday I took the fan clutch out of the Dodge Ram 2500 diesel and brought it to the parts store. The nut part that threads onto the engine was very difficult to spin when cold, so I figured the clutch was bad. Comparing it to a new one at the store, it was just as difficult to turn.

I put the fan clutch back in the truck, started it up from cold, and stuck a rolled up piece of cardboard into it. It shredded it, not slowing down in the slightest.

Not sure how to test one of those fan clutches with a built in thermostat. Seems mine isn't working correctly and causes the engine to take a long time to warm up. Then again, the new part didn't turn freely either.

There is very little info online, mostly people showing the valve that the thermostat is on getting stuck, or the clutch fluid leaking out. Neither of which are my problem.

Put a heat gun on it.
Plus you probably don't need it during winter anyways.

Electric fan conversion!

This is by far the best recommendation.

I recently replaced my clutch fan with electric only to discover my van doesn't need a fan.
It idled for about an hour on a 30deg C day, no fan, heater and AC off and the hottest it got to was 79deg C.
The electric fan is set to come on at 85 but still yet to happen.

People I've told/shown have a hard time believing my two Fords with fan deletes and year-around engine blankets don't run hot. And one also has a "grille block" and the water pump slowed down 40% IIRC.

I don't want to sink much money into the truck as it has a laundry list of problems and has a lot of miles on the chassis (probably around 350,000).

The fan is necessary because I occasionally pull heavy with the truck.

How are clutched fans supposed to work anyhow? It's not connected to the coolant, so how does the thermostat on the clutch "know" when to turn on?

The electromagnetic clutch may not be connected to the coolant lines, but the thermostatic control must do so.


Electric fans not just are more efficient, and more recently becoming cheaper, but they also tend to require fewer maintenance in the long run.


It's still better to have a fan while not needing it than not having and actually needing one.

My clutch fan was triggered by air temp heating a bimetalic strip inside the clutch.
I think others use a viscous clutch and sense coolent temp from the waterpump shaft.

Interesting, but I wonder if that would really be as effective as using some engine temperature parameter such as coolant and/or oil temperatures to trigger the fan.

This is the basic idea as far as I understand them to work. It needs to be up to a certain temp before the clutch engages. But...they're also designed to run when the engine is dead cold, so the fan will be spinning when you first start up and stop running a minute or two later as it warms up. It's a fail-safe, I believe...if the viscous part of it fails, it will get stuck ON.

Don't quote me on it. Just what I picked up in the brief time I drove a truck, years ago.

The fluid in the clutch will drag more when it's cold.
They are actually designed to spin 25% to 30% of crank speed when "off" with the engine bay at operating temperature. When they are cold they probably spin close to 100% of crank speed till the fluid starts to warm up.
Then nearly crank speed when "on".
They temperature of the air behind the radiator tells it when it needs to be on or off.

I'd go electric if one can be had for under $100. Then I'd need to figure out how to trigger the fan based on engine coolant temp.

Junkyard parts should end up a lot less than $100. You'd need a temp switch in the cooling system and a relay to power the fan.