Hyd fan clutch replacement

[ken]

I started getting tired of the leaks and replacing high dollar parts to keep the fan clutch working. So while looking at some civi H1 stuff on the web I saw a 93 model with v belts and a thermo clutch. I searched for the pulley and parts and found they were discontinued. I decided to come up with something on my own. I picked up a extra water pump pulley from the auction site to use for my mods.
From what I read the H1 has a problem with the hood giving the venturi effect while moving. So air is not being forced through the rad very much. I could see this because My unloaded 2 man 998 will engage the clutch every 2miles or so. Even on a cool day at 40MPH.
So with the stock fan not turning much the engine constantly goes through a heating and cooling cycle. When the fan comes on the temp drops. When off it heats up until the fan comes on and starts all over again.
Reading the Hayden site the thermo clutch will turn 30% of WP speed when not hot. So if that the case then It should pull more air when driving therefore allowing the engine to stay a constant temp. I have this fan and clutch on my M1028A1 and it moves enough air when cold to blow the grass under the truck.
I chucked up my auction site pulley, took some mesurements using a spare 6.2 I have on a stand and machined the pulley to make the thermo clutch fit. When the rain stops I'll put it on the truck and see how well it works.

 

[lowell66dart]

Good work. I want to go this route to.

 

[Action]

It sounds like you have some problem that needs to be fixed. And, the stock setup fan spins too when not engaged or disengaged.
I wouldn't just assume that a venturi effect is making your HMMWV got hot so fast.

 

[ken]

I was not having a over heat problem. I installed a 180 thermostat at a switch that kicks on at 195 and off at 180 when I installed the GEP engine. It runs great. Yes the fan does spin when disengaged but it is pretty much in free wheel. They needed the truck to be able to ford water so I can understand why they went this route. But I only need to ford water when a hurricane is here. I can put it back in little over a hour anytime one is near by. They reason I am trying this, is the unreliable stock set up. Any one part that fails will cost twice as much as a new thermo clutch. If it works great, If not I'm only out $35 for the pulley and my time.

 

[Action]

From what I read the H1 has a problem with the hood giving the venturi effect while moving. So air is not being forced through the rad very much. I could see this because My unloaded 2 man 998 will engage the clutch every 2miles or so. Even on a cool day at 40MPH. ​

So your fan coming on every 2 miles isn't because there is a venture effect at the grill, it is because you put in a switch to turn the fan on at 195 degrees.
My engine runs constant at about 185-195. Why did you choose to have the fan kick in at that temp?

​

 

[NDT]

This thread covers what you want to do: https://www.steelsoldiers.com/showt...en-fan-clutch-fit-the-HMMWV&highlight=viscous

 

[ken]

This thread covers what you want to do: https://www.steelsoldiers.com/showt...en-fan-clutch-fit-the-HMMWV&highlight=viscous

Thanks NDT, I remember that thread. That's where I got the info for the 195 switch.
Action: I replaced the thermostat to a 180 and temp switch to keep the engine below 200 deg. I spent too much money on the GEP engine to loose it to a cracked block because it got too hot. I know there are kits out there to help move the hot boiling water out of the rear of the block. But If you reduce the temp below the boiling point you solve the problem.
The reason I wanted to try the thermo clutch is for relilablity and simplicity. Now that I have it installed I'm going to go for a test drive to see how it works.

 

[ken]

I drove it into town last night 11 miles each way. It was 90 deg outside. The temp gage slowly climbed to 180 like normal and stayed there. When I got out to the highway I ran about 52 MPH. I could hear the fan but it was not loud like the stock set up. While stopped at the first redlight in town I could hear the fan start to get louder. It stayed engaged for about 100 yards from the redlight then quieted down. The temp gage never climbed. I ran a few errands then headed home. It never climbed above 180 the whole trip. The belts didn't squeal anymore and seemed to work well. I ran it 28 miles total. So far I'm happy with the way it turned out.

 

[lowell66dart]

Excellent. Can you post part numbers for the clutch and fan that you used? I have a 6.5 Optimizer with the v-belts and I want to do this mod.

 

[Retiredwarhorses]

Once again....diesels rely on heat to run, 180 is NOT the correct running temp range, folks need to get away from thinking gas motors?
as far as your old fan clutch assy, it’s a very simple system, and works well, people just don’t understand it.
your fan going on every 2mins is normal, thats what the time delay module is for.

 

[87m998]

I'm doing this mod also, but converting to a serpentine belt setup at the same time. It's been a huge pain trying to get the right parts.

 

[ken]

Once again....diesels rely on heat to run, 180 is NOT the correct running temp range, folks need to get away from thinking gas motors?
as far as your old fan clutch assy, it’s a very simple system, and works well, people just don’t understand it.
your fan going on every 2mins is normal, thats what the time delay module is for.

I will have to disagree. When the 6.2 came out they had Robert Shaw 370-180 thermostats from the factory. Both of my 1982 GMC's with 6.2' came this way. Old school mechanicaly injected diesels normally run 180 thermostats. They started increasing the temps in the late 1980's trying to meet emission requirments.
I know how the stock fan works. Mine works just fine. I am not having any more problems with it. It preforms like it should. Just like every other Humvee I have drivin. I just don't like it. I only ford water when a hurricane comes through. I can easily put it back in less than a hour if a storm comes. My truck came with a burnt module and valve when I got it along with leaking hoses. Once I replaced the bad parts it has worked well. I have talked with others here who had the same intrest. I am showing them how I did the conversion.

 

[ken]

Excellent. Can you post part numbers for the clutch and fan that you used? I have a 6.5 Optimizer with the v-belts and I want to do this mod.

Yea no problem. I'll start a new thread with a better title so anyone searching in the future can find it easy

 

[lowell66dart]

Thanks. I found a pulley today and just ordered new belts.

 

[Milcommoguy]

Wait till winter and then will hear all about how the heater is cold after a 40 mile trip.

While the TDM plays a connection role in the fan circuit, the fan run / cycle time are determined by the thermostatic switch in the crossover. Included in this is just how well your cooling system is working. We all understand that, radiator, pump, thermostat, heat transfer of coolant, flow, restrictions, working load, ambient temperature and crud, etc. (I am sure I missed some) affect engine temperature.

The thermostatic switch opening and closing (a good and right switch) controlling the cycle time and duration are a direct indication of cooling system performance or lack of.

Go changing out any of the designed components with this or that... fan control along with proper engine temperature will not be in balance. The hysteresis and cooling loop will be all out of wack ie. Switch can't open due to wrong liquid thermostat, engine temp swings wildly, performance suffer and your butt will freeze in winter, not that the heaters work that well anyway.

Here in the Mojave Desert 100 degree days just a cruising around, fan cycle on 1 minute, off five minutes. Come to a stop sign, wait, waiting, on it comes... pull away 200 feet later off it goes. Slow moving, loaded up rig, little air flow, three minutes on, two off. Never the same. Now in the winter 40 degrees out side cruising, hardly ever comes on and then maybe a minute.

The TDM importance is getting the forced fan disengagement (water crossing) and HP boost when down shifting (or more power Scotty) Those two events are timed (about 20 sec.) when initiated.

Without the TDM working can't pass slow pokes and only 20 seconds to switch to boat mode.

CAM

 

[lowell66dart]

We have around two weeks of winter here, two days at a time. Not going to be much of a problem.

 

[ken]

My M1028A1 has the same set up. It's been that way over 10 years . With no problem. The heater works as it should. Every square body civi chevy and gmc with a 6.2 has the same set up. If it works on thousands of other 6.2 and 6.5's it should work here too. I drove it again today. Same result. Engine warmed to 180 and stayed there. I will continue to test it. I'll post any problems I run into.

 

[papakb]

I started to do this changeover about 15 years ago but then got the cooling system running the way it was designed and have never had any more problems with it. I was able to find an old 4 sheeve pulley off of a 6.2 and sawed the lugs off the front of it. I smoothed it out with a disc sander and mounted a thermostatic clutch I'd pulled off of an old Caddy in a salvage yard. I put a 1" long piece of 1/2" conduit in the front of the pulley and the rear of the clutch to keep them centered to each other since the holes were already there. It's been sitting on the floor in the garage since then.

 

[ken]

That looks good. I measured the fan blade to the water pump backing plate. I got 7 7/8. I got 8 3/8 with the thermos clutch. I wanted to put the leading edge of the fan in the same place. So it would not hit the shroud at the top. To bring it back to 7 7/8 inch I had to bore a pocket into the pulley. I could have just faced it off. But since that face meets casting a didn't want to throw the pulley out of balance. I thought I would be ok since the only parts I machined were already machined surfaces. Because I had to cut that deep, the water pump boss will stick through the pulley and into the back of the thermo clutch. This centers the clutch. I used a Hayden PN/2799 clutch and a Derale PN/17120 20 inch fan. I used 1/4-20 1.5 inch long studs with nuts on the back side of water pump flange to serve as lock nuts.

 

[lowell66dart]

Parts ordered. Thanks.