Engine/Transmission (1998.5 - 2002) Can radiator fan clutch operate intermittent??

[groser]

Having intermittent problems with radiator overheating in +90 degree weather while pulling. Yesterday when it happend I didn't hear the fan roar up but on next hill (after radiator cooled) I heard it roar and temp was normal. However the hill it overheated on was a long grade but I would guess 4-5% grade max. This has been going on intermitently in my travels but don't see how clutch can work intermittently. It passes the spin test when cold and stops immedaitely when engine turned off even when engine is around 190 degrees.

Radiator was removed and washed before this trip, wasn't really all that dirty for 72 k miles. Blow by Bottle in original location.

transmission temp (auto) also went up but since they share same radiator coolant I would think this would be normal. It peaked about 220 degrees in transmission outlet line to cooler.





I do think when fan engages it's not as loud as it used to be but then my hearing not improving with age!



Is there any thing else that controls fan speed or engagement other than viscus fluid?

 

[jtwcummins]

Sounds like the fan clutch is going. When fully engaged it makes lots of noise. They do work at a reduced level as they age and get decreasing fan rpm on long pulls.

 

[GregBarnes]

Could be clutch... . but I had a similar problem on my 99 2500 4x4 and turned out to be the tstat.

 

[ASimpson]

My Truck Does This Only When It Gets Hotter Than Normal This Time Of Year If Im Pulling It Hard The Fan Will Get Louder For A Couple Minutes Till It Cools Down Then You Wont Hear It Untill It Starts Getting Hot Again. Almost Like A Big Rig. Not Sure How It Would Engage Or Disengage The Clutch But Sounds Exactly Like Whats Happening And It Only Does It When Hot.

 

[LOtero]

Fan cluthches are supposed to only operate full boar when needed, (pulling hills, under load, or running hot. ) when the clutch senses the coolant getting hot it locks up the clutch, when cruising at speed it doesent need the fan so it slips the clutch. more for noise than anything,