Question for the car gurus...clutch driven radiator fans

[public servant]

Should a clutch driven radiator fan become harder to turn by hand when a vehicle reaches operating temperature as compared to when it's cold?

My 2002 Dodge Dakota 4.7L ran hot the other day. I replaced the thermostat and radiator cap. This seems to have cured the problem but I want to make sure. While researching I saw a video where a guy had an identical issue and his mechanic blamed the clutch fan. The mechanic reached his diagnosis because the fan was as easy to turn hot as it was cold, as is mine. He claimed there should have been considerable resistance turning the fan manually once it gets hot.

I don't think at this point it's head related as I saw no foreign substances in the antifreeze, nothing in the oil, no antifreeze or smoke coming from the tail pipe, the plugs are spotless and it still runs really strong.

So I'm questioning if it may have been at least in part the clutch fan.

Also, is it possible to convert from the clutch fan to a standard mechanical fan? I don't like electric fans so I'd just change the clutch fan if necessary.

Thank you in advance for any insight.

 

[eldirector]

Yes. Thermostatic fan clutches should turn pretty freely when cool (not freewheel, but turn easily), and offer much more resistance when hot (not locked up, but much stiffer). They are easy to replace, and not expensive.

I would not recommend switching to a "hard mount" fan. Not only do they draw the same amount of air when cool as when warm (potentially not letting the engine warm as well/quickly), they also offer a good bit of resistance when running at speed (not letting air flow as freely through the radiator). You can actually cool LESS with them, in some situations.

 

[giovani]

Unless you want your dakota to sound like a WW 2 era jeep , don't put a solid fan on it.

a fan clutch is not bad to replace and only a $50to$70 item, if I suspected one on my truck I would replace it.

on high mile vehicles with AC all the bugs , feathers, other debris builds up over time between the rad and the condensor and will decrease air flow.

We used to pull radiators and clean out the fins with a garden hose and compressed air

 

[Bigtanker]

When you change the fan clutch, (which it needs to be changed) make sure to get (rent) the fan clutch wrench set. Without the correct wrench, it can be next to impossible.

 

[Caleb]

Don't let that clutch fail on you, just ask me why...

 

[public servant]

Why?

 

[heavyhitter1k]

Clean the rad and see where that gets you...higher mileage means it's prob dirty. Won't cool as efficently

 

[Caleb]

...because the stupid thing will break off and shred your radiator, bounce around the engine compartment, drop out from underneath the car, and right on down the road.

 

[Hohn]

You do indeed want a clutched fan. Or an electric fan than is PWM controlled-- even better.

Most fan clutches work by means of a silicone-based fluid inside them that thickens as they warm up. The thicker the fluid (hotter), the less slippage the clutch allows and the more fan RPM you'll have relative to engine RPM.

The downside to these clutches is that they never fully lock up when hot (they always slip), and they never fully release when cold (they always turn the fan). Electric fans are much better in this regard, and that's the main reason most OEM fans are now electric.

There's also a good bit of value in divorcing fan speed from engine speed-- like trying to have the A/C work well when idling and parked.


Unless you plan on pulling a heavy trailer up the Grapevine in 90+ temps at very slow speeds, an electric fan is going to be plenty of air.

 

[public servant]

...because the stupid thing will break off and shred your radiator, bounce around the engine compartment, drop out from underneath the car, and right on down the road.

 

[Kirk Freeman]

Did you inspect the radiator to ensure nothing like an Arby's bag plastered itself to it causing your temp to run high?

Ask me how I know to do this.

Are you hauling horses or something heavy? Why the clutch fan?

BTW, water pumps will also fall out of Monteros as you are driving down the road and make awful rackets on 465.

 

[public servant]

Did you inspect the radiator to ensure nothing like an Arby's bag plastered itself to it causing your temp to run high?

Ask me how I know to do this.

Are you hauling horses or something heavy? Why the clutch fan?

BTW, water pumps will also fall out of Monteros as you are driving down the road and make awful rackets on 465.

Only the usual dead bugs. But I'll fire up the compressor later and see what I can blow out.

The clutch fan was standard equipment. The truck has the towing package but I haven't hauled anything with it yet. We were driving thru southern KY the first time it got hotter than normal. We were in bumper to bumper traffic in Pigeon Forge the second time (I was keeping the AC off since the first issue). Then I replaced the radiator cap. No issues after that and the gauge showed it running slightly cooler than normal before the incident. Then I replaced the coolant and the thermostat when we got back home.

I discovered the fan issue while researching known problems and fixes. I discovered my fan turns as freely with it hot as when it's cold. Which apparently it's not supposed to do. According to the videos I watched and the advice from all the great members here.

 

[Caleb]

True story...Now I've been wanting to switch my jeep from clutch fan to electric fan, one of these days...