I have thought for some time that my fan is on all the time. I never hear a difference in sound or fan noise. I also have a little sound at low rpm that I think is the fan in direct drive. Any time stopping the truck, cold or hot the fan is real stiff to turn. It also has some slop if you wiggle it. How to tell if it is constant on?

 

Hmm...not a good sign if there is some slop in it.......is the fan main bearing sloppy or is the clutch sloppy? I know when the fan clutch locks up on mine it sounds like there is a helicopter trapped under the hood - it is very loud and there is a noticable hp loss, though slight, it is noticable.

The way I have checked clutch fans in the past is to hold a small piece of wood in the fan blades with the engine off and then I get someone to start the truck. This is not as dangerous as it sounds.....if the clutch is too tight, it will knock the wood out of your hand....you should be able to stop the fan from spinning easily if the air off the rad is not hot enough to engage it. To me it is obvious if the clutch is too tight - the fan is loud....when that sucker is locked up it will darn near blow the cap off my head at idle!

 

HiD, I would suggested using a old radiator hose or a old garden hose to do that. Rubber is more forgiving if it does turn on you...

I'm surprised that is a old Dodge trick that I was taugh as a kid... And it's still used!

 

If it is stiff even when cold, toss the clutch and get a new one, they aren't cheap either!! But then again neither is diesel these days!!

Tom

2001.5 2500 4X4 5-Spd LB QC Black. Catcher ECM, DD Stage-1's, AFE, Bully Dog 4" pipe, ATS Exhaust Manifold, Silencer Ring MIA, JAKE Brake w/shifter switch, Geno's Banjo's, 3 Autometer's on the A-Pillar, Gear Vendor's O/D, Firestone Air Bags, Redline Oil throughout.
Soon-to-have 14cm Turbo Housing and RASP Pump (Thanks Olee!!)

 

pizza box or similar shaped cardboard box works for me.

 

i have had my truck for over a year, the first time the fan ever kicked in was when i hooked the gooseneck up in texas, it sounded like a plane takin off under the hood!!! it startled me because i never heard it before, but it came on and went off and is working fine. it never came on once we hit cold weather, even towing home.

i guess what i am saying is, if it kicks on you should hear it, if its locked up all the time it should sound really loud first thing when cold taking off.

 

Easy way to check it is to have someone rev the engine up then shut it down while you're watching the fan. It shouldn't stop suddenly nor freewheel, just five or so revolutions after the engine stops would be considered fine.

Replacement clutches aren't all that much, I paid $59 not all that long ago from Napa. Suppose if you want to pay more you can go to the dealer.

 

Well I do have to replace it, mine cound not freewheel. I know this about viscous fans from other replacements. The factory produces temperature controlled fans, the aftermarket are generally rpm based fans. I do have an extra here, not sure of the condition. Will probably put it on today.

 

I have never- ever heard mine . I will get my dad to check it while I getting my ez off his truck.

 

When mine worked right, it did sound like a plane taking off. Definately noticeable. Now it won't kick in unless the RPM's drop down under 2000. Does that sound like the clutch going out?

 

Never heard mine either.

 

Well I pulled it today, had another one from a 96 12 valve. The 12 valve fan clutch is smaller and has a bigger fan. Not in diameter but my fan blades are 1/2 inches narrower with a larger clutch. So not being sure of the installation, I ordered a new on that will be in tomorrow.

The truck is so quiet with no fan, and smooth. Gotta run a load tonight, should have no problem with no fan, I won't be idleing any and it is night.

Also I had a little rumble noise at low rpm, almost like a power steering growl that I was trying to trace down. It was the fan, I sort of thought so, now it is gone with the fan off the truck.

There is also a tip here if you have overheating problems climbing hills with a load, the bigger fan is on the late 12 valve engines. Might help a problem.

 

I purchased a new one, it is the smaller one and I put the 12v fan on it. It turns freely, is quiet and smooth, a definate improvement. Ran it two days with no fan, never got any extra heat except it got a little bit high sitting intraffic with the air on.

 

Good info, HID--thanks for the tips!