Will an old fashioned GM speed driven fan clutch fit the HMMWV?

Will the old GM fan style clutch fit the HMMWV, AND was the purpose of the hydraulic fan clutch only to allow a simple way to turn off the fan when fording water?

Just curious.

Also, how many of you guys switched to electric fans mounted directly under the radiator to free up space?

Again, just curious.

I'm not looking to modify at this time... just trying to better understand this vehicle and its engineering for future use.

T

RWH will shoot me but yes it can be done, I put the viscous clutch on mine a very long time ago because I hated having the crap scared out of me every time the hydraulic clutch came on. Use the H1 fan, and the clutch from a mid 90s Chevy 1 ton. You also have to grind the protrusion on the pulley off.

Edit: Dug through my truck build documents from 1992, the p/n of the clutch I used is 05939545. Still a good number in 2017. Fan is 05939560. Hummerpartsguy lists it. Both are parts used on the H1, I just verified in the H1 parts book.

i have the viscous clutch on my REV. The fan kicks in just like the hydraulic fans do. When it turns on, I know it!

Awesome information.

Thanks guys!

papakb said:

I found when I mounted the fan to the clutch that a short piece of conduit fit precisely in the center aligning the fan to the clutch. This can be a little tricky after you've ground off the protrusions.

Kurt

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That is really great information.

How do you guys de-activate when fording in water? Just remove the whole thing?

The water will probably be gone before you r and r a Humvee fan blade on the trail!!!!

Thanks for the exact information with parts numbers.

Seems like your set-up is easier to service in emergencies.

Deactivation in water fording might be an issue, but how often does a person forde water?

T

Hit the pedal to the floor real quick. It should disable the fan for a few seconds, if it is on. It shouldn't activate once in the water. The fan does spin with the motor, even when it is off, but it can be stopped easily. If you don't hear the really loud howl, it probably isn't on, but whill be spinning slowly.
Do NOT keep the pedal on the floor while fording.

When entering water the engine temp drops fast and the fan should turn off due to cooler engine temp regardless of the type of clutch.

kc5mzd said:

When entering water the engine temp drops fast and the fan should turn off due to cooler engine temp regardless of the type of clutch.

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kc5mzd, if you enter water with a fan spinning it may tear the fan apart, frequently with the radiator (not sure if the angled HMMWV radiator offers some protection).

Just ask guys who 4WD in wet areas and on beaches.

Most guys who ford water remove the fan first. (Common topic on Land Cruiser forums).

Best,

T

Action said:

Hit the pedal to the floor real quick. It should disable the fan for a few seconds, if it is on. It shouldn't activate once in the water. The fan does spin with the motor, even when it is off, but it can be stopped easily. If you don't hear the really loud howl, it probably isn't on, but whill be spinning slowly.
Do NOT keep the pedal on the floor while fording.

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action is correct, that thing on the side of the injection pump is the fan cutouff switch, used for passing, but as well...fording.

I hope the fan tore apart due to turning at high rpm when hitting the water - I would not expect that to happen under 1000 or 1500 rpm???

If the hyd clutch is engaged upon entering deep water at any engine rpm, the fan blades will shatter.

YES-- a fan grenade, with shrapnel everywhere! Possibly the radiator.....

So I guess if you have a viscous clutch you would need to stop, run the engine around 1000rpm till the fan cools everything down enough to shut off before entering the water? Sounds scary and messy...

A lot of guys down here have late model ford, chevy, dodge and have no problems with water. If they hit it to fast that's when problems arise. I think that if you entered slowly you would be fine. I just did a waterpump replacement on my personal truck this week and would have switched over to the viscous, if I had remembered... DOH--Also, when I mess with the fan shroud, I move it back(towards the front of the truck) and up. That gives the most clearance from fan contact. All the fan shrouds I've seen sit low on the top and are close to the blade. I replace the fan blade with a new kascar unit. I have 4 old fan blades in my garage and 1 apple core-- no blades left on it.

Trying to picture this... You have a pic to share?

Not mentioned is that the HMMWV fan deactivation trick only works with later models, according to what I've read in the TM and what I've experienced. My M998 a0 doesn't deactivate on command, so SOP is to enter anything deeper than 20" slowly.
Bulldogger

Will the viscous clutch engage at lower engine temps? I swapped to a 180 thermostat and would like the fan to keep it that cool. My CUCV runs at 180 this way. I have forded my M1028 many times after hurricanes and tropical storms. A Few times for miles. I enter the water and stop just before the front bumper gets wet. This puts the oil pan in the water and cools the engine fast. If the fan was engaged you can hear it slow down. Then enter the water and carry on with the engine just above idle. I have had no problems fording like this. But with a plastic fanon my 998 I do worry.