Mechanical engine fan in '05 Durango vs '05 Grand Cherokee

You may want to post this in the truck section, I dont work on Jeeps/Trucks
but im pretty sure that the fan on the Jeep operates off hydraulics from
the P/S pump and not a mechanical fan

Glenn Beasley
Chrysler Tech
 >> Stay informed about: Mechanical engine fan in '05 Durango vs '05 Grand Cherokee 

On your Hemi, don't you think the loudness is the clutch engaging, making
the primary engine fan become loud?

On my Durango 4.7L, the fan is quiet as well normally. It's just on startup
that I hear the hurricane for about the first minute of operation, or I may
hear it for a few seconds if I've been sitting at a red light for a
minute -- the heat builds up a bit making the clutch engage.

In the past I've read that on the ordinary viscous coupling the silicone
fluid has to work its way out of the clutch grooves so that the fan can spin
more slowly. From that point on, only heat should cause the viscous
coupling to engage, making the fan louder -- such as when towing.

It's no big deal, of course. But that Jeep 4.7L sure is nice and quiet on
startup, so it got me wondering. Got me thinking maybe I it's just a
different clutch design and I might switch it. Most likely there's some
complication that makes a swap impractical or impossible anyway.

Marcus

"miles" wrote in message

> Marcus wrote:
>> The mechanical engine fan is very noisy on startup in my '05 Durango
>> 4.7L -- sounds like a hurricane on startup and takes a minute to quiet
>> down. I realize this is normal and why it happens.
>>
>
> On my 2004 Hemi Durango the fan on startup or normal driving is very
> quiet. When the engine gets a bit hot such as when I tow up hill in the
> summer the auxiliary fan turns on and it is VERY loud.
 >> Stay informed about: Mechanical engine fan in '05 Durango vs '05 Grand Cherokee 

I have 2 older Dakotas (98 and 00) and when they are cold the fan will do
that. It also does it when the engines get to a higher temperature to where
the clutch on the fan engages and the fan spins faster. That is normal and
by design. It's when the fan makes squealing, grinding, or other "non-wind"
related noises or stops turning altogether, is when you need to start being
concerned. The clutch fan is just that - it has a sealed hydraulic clutch
that engages when engine temperature gets high enough for it to engage. You
can turn your fan blade by hand whith the engine off. There should be
resistance to it. If there is none you may want to get it checked out.

"Marcus" wrote in message

> On your Hemi, don't you think the loudness is the clutch engaging, making
> the primary engine fan become loud?
>
> On my Durango 4.7L, the fan is quiet as well normally. It's just on
> startup that I hear the hurricane for about the first minute of operation,
> or I may hear it for a few seconds if I've been sitting at a red light for
> a minute -- the heat builds up a bit making the clutch engage.
>
> In the past I've read that on the ordinary viscous coupling the silicone
> fluid has to work its way out of the clutch grooves so that the fan can
> spin more slowly. From that point on, only heat should cause the viscous
> coupling to engage, making the fan louder -- such as when towing.
>
> It's no big deal, of course. But that Jeep 4.7L sure is nice and quiet on
> startup, so it got me wondering. Got me thinking maybe I it's just a
> different clutch design and I might switch it. Most likely there's
> some complication that makes a swap impractical or impossible anyway.
>
> Marcus
>
> "miles" wrote in message
>
>> Marcus wrote:
>>> The mechanical engine fan is very noisy on startup in my '05 Durango
>>> 4.7L -- sounds like a hurricane on startup and takes a minute to quiet
>>> down. I realize this is normal and why it happens.
>>>
>>
>> On my 2004 Hemi Durango the fan on startup or normal driving is very
>> quiet. When the engine gets a bit hot such as when I tow up hill in the
>> summer the auxiliary fan turns on and it is VERY loud.
>
>
 >> Stay informed about: Mechanical engine fan in '05 Durango vs '05 Grand Cherokee 

Thanks, but the question was why my '05 Grand Cherokee 4.7L does not make
that startup hurricane noise. The Jeep's 4.7L is quiet on startup while the
Dodge 4.7L has the hurricane noise. I would assume the two 4.7L engines
would be basically identical, especially for something as mundane as the fan
coupling.

I have the manual for the Dodge and it uses a standard viscous coupling, but
I don't have a manual for the Jeep yet. I thought perhaps someone here
might know how the Jeep 4.7L runs its mechanical fan, assuming it doesn't
use an ordinary viscous coupling like the Durango uses.

"Abby Normal" wrote in message

>I have 2 older Dakotas (98 and 00) and when they are cold the fan will do
>that. It also does it when the engines get to a higher temperature to
>where the clutch on the fan engages and the fan spins faster. That is
>normal and by design. It's when the fan makes squealing, grinding, or
>other "non-wind" related noises or stops turning altogether, is when you
>need to start being concerned. The clutch fan is just that - it has a
>sealed hydraulic clutch that engages when engine temperature gets high
>enough for it to engage. You can turn your fan blade by hand whith the
>engine off. There should be resistance to it. If there is none you may
>want to get it checked out.
>
> "Marcus" wrote in message
>
>> On your Hemi, don't you think the loudness is the clutch engaging, making
>> the primary engine fan become loud?
>>
>> On my Durango 4.7L, the fan is quiet as well normally. It's just on
>> startup that I hear the hurricane for about the first minute of
>> operation, or I may hear it for a few seconds if I've been sitting at a
>> red light for a minute -- the heat builds up a bit making the clutch
>> engage.
>>
>> In the past I've read that on the ordinary viscous coupling the silicone
>> fluid has to work its way out of the clutch grooves so that the fan can
>> spin more slowly. From that point on, only heat should cause the viscous
>> coupling to engage, making the fan louder -- such as when towing.
>>
>> It's no big deal, of course. But that Jeep 4.7L sure is nice and quiet
>> on startup, so it got me wondering. Got me thinking maybe I it's just a
>> different clutch design and I might switch it. Most likely there's
>> some complication that makes a swap impractical or impossible anyway.
>>
>> Marcus
>>
>> "miles" wrote in message
>>
>>> Marcus wrote:
>>>> The mechanical engine fan is very noisy on startup in my '05 Durango
>>>> 4.7L -- sounds like a hurricane on startup and takes a minute to quiet
>>>> down. I realize this is normal and why it happens.
>>>>
>>>
>>> On my 2004 Hemi Durango the fan on startup or normal driving is very
>>> quiet. When the engine gets a bit hot such as when I tow up hill in the
>>> summer the auxiliary fan turns on and it is VERY loud.
>>
>>
>
>
 >> Stay informed about: Mechanical engine fan in '05 Durango vs '05 Grand Cherokee 

Marcus wrote:
> On your Hemi, don't you think the loudness is the clutch engaging, making
> the primary engine fan become loud?

Dunno. All I know is that when the engine starts to get warm I hear a
VERY loud roar and the temp quickly comes down and the roar stops.
 >> Stay informed about: Mechanical engine fan in '05 Durango vs '05 Grand Cherokee