Why do severe duty clutch fan always ROAR?

[vindex1963]

I replaced the severe duty clutch Hayden 2796 in my 1995 Grand Cherokee 4.0L with a standard duty from a Cherokee Hayden 2625 because it killed my gas milage, power and the never-ending constant ROAR. The severe is the only option for the GC unless you go with Cherokee, same motor and the GC doesn't weigh that much more. I've read postings about the fan blades don't have enough "bite" or wind resistance to release the severe clutch so it free wheels.

The original clutch was shot that's why I replaced it with the only GC option of the severe.

My question, why doesn't the severe free wheel like the standard until it needs to lock up? The standard is keeping my jeep just as cool as the severe but has way less lockup speed so towing might be a problem, I don't know yet. My milage went from 18 to 25 just changing the clutch so it's substantial and passing power is greatly improved and the constant roar is gone.

 

[Rand]

1995 grand cherokee with 25mpg? thats a unicorn.

 

[blufeb95]

1995 grand cherokee with 25mpg? thats a unicorn.

Only if you're only going downhill in outerspace.

 

[vindex1963]

That's what I'm getting, but that's not the question

 

[blufeb95]

You've got to be calculating it wrong no jeep with a 4.0 gets 25mpg, your question revolved around the fan clutch affecting mpg and you stated your car is getting a level of fuel economy that is impossible for your vehicle.

 

[Jethro_Bob]

To keep you jeep cool while idling, rock crawling, or any other high rpm low speed uses. Pretty much any time you use low range on the transfer case.

 

[vindex1963]

You've got to be calculating it wrong no jeep with a 4.0 gets 25mpg, your question revolved around the fan clutch affecting mpg and you stated your car is getting a level of fuel economy that is impossible for your vehicle.

Last tank calculated 23mpg, I had the AC on.

so........why is it that severe fan clutches roar like a school bus? They can't make them like the standard duty that free wheels until engaged or is it the fact the fan blades don't provide enough resistance to dis-engage the clutch.

 

[MNgopher]

Reading your original post, you replaced a bad clutch and in your words, the replacement roared all the time. You then replaced it with a different part.

How do you know the original replacement part was good out of the box? My experience with fan clutches in my '88 Cherokee was that quality, even then, was very hit or miss right out of the box. Hayden units got me some that were as bad as the failed ones, and others that were constantly locked up.

As to why a unit like this would, in your words, roar - because its doing its job which is to engage the cooling fan at a higher duty cycle, which means the fan is going to move more air, which means more noise. You should hear the fans on the trucks we use at work when they start working...

Had an '88 Cherokee with the 4.0. On a perfect day it might hit 21 mpg. Friend had a grand with the 4.0, and it always did worse than my Cherokee...

 

[clinebarger]

Hayden severe duty clutches are very aggressive no matter the application.

 

[oilcandave]

...not a bad thing to cool the radiator down...might help with the tranny cooler which is on the cool side of the radiator..

 

[Nick1994]

Because it needs to be moving lots of air.

My 4.0L runs hot in the summer not only on high load/RPMs but at low speed/low RPMs too. In my case, it didn't help though, so air flow wasn't the issue.

 

[vindex1963]

Because it needs to be moving lots of air.

My 4.0L runs hot in the summer not only on high load/RPMs but at low speed/low RPMs too. In my case, it didn't help though, so air flow wasn't the issue.

This is a 90+* day on a long uphill 225* overdrive bypassed. Not all that hot considering 210* is considered normal. 10 miles of a pretty steep grade 6%. My 1995 has 75,000 miles.

 

[Lubener]

Increasing air movement means more noise.

 

[dlundblad]

I wonder if you can get the GM 11 blade plastic fan and a 2006 Hummer H3 fan clutch to work. It’s tight, but they do fit the WJ with the 4.0.

I think I have a Hayden clutch in my WJ, but I know it’s not severe duty. I just have the regular 5 blade steel fan with the offset blades. I think it was used in other Dodge and Jeep with the 5.2 V8. Zero issues and minor power loss.

 

[ls1mike]

I don't know why, but I can tell you on my 89 GMC 1 ton that thing was loud. Always worked well and kept the truck cool, but you knew it was there. The one in my 2002 2500HD was pretty quiet as are the ones in my kids 97 K1500 and my 2017 3500HD

 

[vindex1963]

I wonder if you can get the GM 11 blade plastic fan and a 2006 Hummer H3 fan clutch to work. It’s tight, but they do fit the WJ with the 4.0.

I think I have a Hayden clutch in my WJ, but I know it’s not severe duty. I just have the regular 5 blade steel fan with the offset blades. I think it was used in other Dodge and Jeep with the 5.2 V8. Zero issues and minor power loss.

Mine has the 7-blade steel fan.

 

[wtd]

I think I installed the severe duty one in my 98 Chevy K3500 with the 454 and it was super loud when it was new. After about 14 years now, it's pretty quiet. The truck still stays cool so I guess it's still working.

 

[nthach]

Never used Hayden but the bimetallic element should allow the clutch to “bypass” when it’s not hot enough. Aftermarket fan clutches aren’t built to the same precision as an OEM one from the likes of Aisin/Behr(Mahle)/Harrison Radiator/Hitachi.

 

[Rhymingmechanic]

I don't know if there's finer detail available about your part number, but I found this information in the Hayden catalog:

Fan Clutch Types and Specs

 

[jeepman3071]

Reading your original post, you replaced a bad clutch and in your words, the replacement roared all the time. You then replaced it with a different part.

How do you know the original replacement part was good out of the box? My experience with fan clutches in my '88 Cherokee was that quality, even then, was very hit or miss right out of the box. Hayden units got me some that were as bad as the failed ones, and others that were constantly locked up.

As to why a unit like this would, in your words, roar - because its doing its job which is to engage the cooling fan at a higher duty cycle, which means the fan is going to move more air, which means more noise. You should hear the fans on the trucks we use at work when they start working...

Had an '88 Cherokee with the 4.0. On a perfect day it might hit 21 mpg. Friend had a grand with the 4.0, and it always did worse than my Cherokee...

My 1990 Cherokee Limited with 4.0 hit 22 on the highway a few times, but the pre-HO 4.0 engines have some differences over the later years. The transmission also had the "comfort" button which allowed it to have lower shift points which saved fuel. I think everything after 1991 or 1992 was just in "power" mode.

Severe duty clutches will roar all the time, they are designed to move more air. I used one once on one of my Jeeps and took it out after a week. My Jeeps never ran over 210, even when towing on a 100* day.

I set them up this way:
-OEM Mopar fan clutch (Hayden if you can't find one)
-Hesco high flow thermostat housing
-Stant Superstat 195* thermostat
-CSF 3 row radiator
-B&M plate style transmission cooler routed in a way so that it bypasses the radiator
-Redline water wetter
-Mopar water pump (GMB if you can't find one)

All of the above mods made it run consistently cooler, especially on my 2000 XJ that had heat soak problems due to the cali emissions cat convertors under the hood baking everything. The transmission cooler radiator bypass is huge for the automatics, as both the AW4 behind the XJ and the 42RE behind the ZJ make a lot of heat that gets put into the coolant through the normal in-radiator trans "cooler".

My 1998 Wrangler with 4.0/AX-15 ran significantly cooler with all the stock cooling system stuff than my automatic XJ Cherokee did.