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Old 03-01-2008, 09:24 AM   #1
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Clutch Fan Tips

My clutch fan locked itself up during a recent trip and does not freewheel when the engine is cool. Makes a LOT of noise. I found the following tips when browsing a GM Motorhome forum and thought it would be worth sharing...

I thought the part about proper right-side-up storage would be valuable info!
.................................................. ....................................................
How do I know if my Fan Clutch is working?
The Wiley Fan Clutch by Chuck Arnold
http://www.thepowershop.com/fanclutch.htm


From time to time some motorhome owner will call me and say that he needs help because his
transmission won't shift out of second gear. Hearing this complaint, I usually ask "Is this motorhome new
to you?" Often the response is that the person has had the coach only a short time. Usually the rig is not
equipped with a tachometer (rpm gauge) and the owner or driver is misinterpreting a loud noise they are
hearing as being excessive engine rpm. I ask them if the noise goes away when they go downhill or when
the motor is cold. I ask them if it is worse or starts when they go uphill. If they say yes to these
questions, then all that is occurring is that they are hearing the normal sound of the fan clutch doing its
intended job.



The Fan Clutch is a device which permits the engine to avoid wasting horsepower by sucking cooling air
through the radiator when it is not needed. Once the motor is hot enough to need more cooling than is
provided by the normal flow of air caused by moving down the road, the fan clutch engages, causing the
fan to spin, creating more air flow to cool the engine down. Fan Clutches contain a heat-activated valve
and a special silicone fluid which permit the fan to freewheel up to a certain temperature and then to
lockup and move much more air above that temperature. This action reduces noise, saves gas, and
makes more power available to the wheels under lighter load operation. Fan clutches can be engineered
to come on at specific temperatures. Most tow vehicles and motorhomes have fan clutches which
engage when the air coming through the radiator is between 200 and 205 degrees. If you are standing
next to a running engine and the temperature is rising through the 200 degree area you will notice a
significant change of the amount of air being moved by the fan when the Fan Clutch turns on. It will seem
like a switch turned the fan on. One second the clutch is off and the next you will hear the noise and
notice much more air. (A very few clutch fans come on gradually rather than quickly)



It is a good idea to make a point of being aware of what your fan clutch sounds like and when it turns
on. Know by outside temperature, steepness of hill, amount of load, and reading on your dash
temperature gauge when it should turn on. As time goes on you may encounter a fan clutch failure or
some other problem which may lead to engine overheating. If you no longer hear the familiar sound of
the fan clutch engaging when it should, you can predict problems with overheating just around the
corner.



You can recognize a failed fan clutch in a number of ways. Look for excessive play in the bearing on the
clutch shaft and for evidence of the silicon fluid leaking out. If you inspect the front of the clutch
assembly with a light and mirror and see a greasy substance around the thermostatic spring a failure is in
progress. If the motor is at operating temperature and running at 2500 rpm or so and is quickly shut off
while someone watches the fan and the fan spins more than 4 or 5 seconds the fan clutch is bad. The
Fan Clutch does not have to be engaged for this spinning test. You can carefully cause a controlled
overheating of the engine by blocking the radiator with cardboard and monitoring the temperature while
idling in park with the brake on. If you are measuring the air temperature behind the radiator with a
thermometer and the temperature gets above 210 degrees without the Fan Clutch engaging and a
noticeable increase in air flow occurring, the Fan Clutch is bad. Be very sure to watch this procedure
carefully and remove the cardboard when done. You could ruin your engine if you forgot to remove the
cardboard. Some Fan Clutches are noisy when cold and quiet down when they warm up a bit. As long
at the Fan Clutch works properly at higher temperatures this is nothing to worry about. Be sure to avoid
the moving belts and fan. Most mechanics can remember a careless moment when they almost were
injured by the spinning fan. Stories of lost hands and fingers are a grim reminder to be very careful
around machinery.



It is very important to note that the handling of new Fan Clutches and used ones removed for other
repairs is critical. All new Fan Clutches come in boxes marked with a "This Side Up" arrow. Fan
Clutches which are not stored correctly before installation may never work properly. If you get a new
fan clutch and distrust how it has been stored, it is a good idea to let it stand on your shelf in the proper
orientation for 24 hours or so to avoid trouble. A used fan clutch which is taken off for repair of other
engine components must be stored in its normal running vertical position until it is reinstalled or it will not
work properly again. I learned this at a Delco-sponsored air conditioning school.



I was one of a hundred or so mechanics in the class who were embarassed to learn that we had been ruining every Fan
Clutch we had ever removed. If you have worked on engines and noticed occasions when you had
overheating occur after a repair in which the Fan Clutch was laid flat on the floor for a few days, you
have had this experience too.


Know your Fan Clutch. Observe it doing its proper job and treat it right when servicing, and your travels will go better during the RV'n part of your life.
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Old 03-01-2008, 09:33 AM   #2
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Thanks Auretrvr!
Great info

Had I only known about this 7 years ago

Best,
Michael
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Old 03-01-2008, 09:37 AM   #3
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Good informational post!
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Old 03-01-2008, 09:40 AM   #4
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My fan clutch is also locked up and I am just waiting for warmer weather to replace it.
I have also been told by an Isuzu mechanic that if the clutch is locked so the fan cannot free wheel, it will actually caues the engine to run warmer than usual.
Sounds strange though. Seems like the extra air would make the engine run cooler.
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Old 03-01-2008, 08:48 PM   #5
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Electric fan clutch

My very first car was a 1948 Ford. I got it in 1954. Installed on it was an ELECTRIC fan clutch, thermostatically controlled. I do not ever remember having any overheating problems during the 5 years I had it. Off course, being young I had to play with it. I rigged it up with a switch on the dash to be sure to ensure a little advantage during the ocassional street drag 'challenges' . What happened to the electric clutch idea? I replace todays clutches every 2 or so years.
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Old 03-01-2008, 08:52 PM   #6
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Quote:
Originally Posted by cooperhawk
My fan clutch is also locked up and I am just waiting for warmer weather to replace it.
I have also been told by an Isuzu mechanic that if the clutch is locked so the fan cannot free wheel, it will actually caues the engine to run warmer than usual.
Sounds strange though. Seems like the extra air would make the engine run cooler.
The engine has to work harder than it should to force the air through the radiator.
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Old 03-02-2008, 04:52 PM   #7
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Definitely an interesting post on how to deal with the fan clutches.

So far ours seems to be working but my long term plans are to replace the mechanical fan with 2 electric ones. Seems to be the method of choice for a lot of people.

Great post, thanks!

Brad
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Old 04-10-2008, 07:26 AM   #8
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Fan Clutch Installed...

Cost $78 at NAPA. I placed some kraft paper in front of the fan to protect the radiator, but there was plenty of room to maneuver and it went pretty smoothly.

The article about the danger of improperly stored fan clutches may be obsolete. The instructions with mine said that the fan would recover from being stored upright and would work fine after a little bit--and that's what I saw with this one.

A big relief in the noise department!
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Old 05-29-2008, 02:18 PM   #9
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What can happen when a fan clutch engages inappropriately? I just had mine replaced on our Dakota, and it engages a lot when it should not (at starting, initial take-off, and taking off from a light or stop sign). It seems to work correctly otherwise. I have to go on an 1,800 mile trip starting tomorrow, the dealership did not order the part in to fix it (I took it back in enough time) because the foreman wanted a "second opinion" from the guy who did the work. He assured me that there would be no problem on my trip (What!?! He originally said he wasn't sure of what could be causing the problem so he wanted a second opinion!).

What else would make a fan clutch engage like this? And will it hurt my truck on a 3-day, 1,800-mile trip???

This makes me very nervous, but I really have no choice.

Susan
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Old 06-01-2008, 07:17 AM   #10
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Our fan started to be always "on"... any tips? what should I do? Thanks
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Old 06-01-2008, 07:43 AM   #11
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vehicle? engine? electric or clutch?
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Old 06-01-2008, 12:09 PM   #12
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1989 345 LE with the Chevy 454 . AM not sure what you mean by "electic or clucth?"

The way it all started:
We were driving, and the fan would come on and off (as it should) then suddenly it just went into a really "high" gear -sounded twice as loud and stayed there the whole rest of the trip.
A few days later, the same thing happened....

Now it seems on, and loud, all the time....
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Old 06-01-2008, 04:52 PM   #13
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Chris,

You're definitely going to have to replace your fan clutch. I'm fairly certain you can get the clutch from most good parts houses. Its something I haven't as yet had to replace on our 310 so I can't give real good advise. I know there are a bunch of posts on the forum about replacing it.

I'm kinda guessing here but I'm pretty sure you can replace it by working from inside the motorhome (which is good because you can run the roof top A/C while working!). You'll have to lay on top of the engine and work mostly by feel. I believe there should be four bolts holding the fan to the clutch and four more bolts holding the clutch to the water pump.

I always carry and nice soft mat that I can lay on top of the engine. Makes it a lot more comfortable to work that way.

Hopefully someone will chime in with more specific directions.

Good luck!

Brad
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Old 06-01-2008, 09:17 PM   #14
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hey Brad, you mention "water pump". do you know where the water for that pump is? I found a black container near where the washer fluid container is...could that be "it?" what kind of fluid goes in there?

Thanks!

Christophe
Also, if anyone has any more advice etc ... could it be a fuse? could it be the thermostat? Where are these?

Thanks!
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Old 06-01-2008, 10:18 PM   #15
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Quote:
Originally Posted by gypsychris
hey Brad, you mention "water pump". do you know where the water for that pump is? I found a black container near where the washer fluid container is...could that be "it?" what kind of fluid goes in there?

Thanks!

Christophe
Also, if anyone has any more advice etc ... could it be a fuse? could it be the thermostat? Where are these?

Thanks!
Chris,

There is nothing electrical about the fan clutch. Its purely a mechanical device. The water pump is basically smack dab in the upper center of the front of the engine.

That black container is most likely your power steering fluid reservoir. The fan clutch assembly is located between the radiator and the front of the engine. There are only two ways you're going to be able to see it. The first is to lay on the ground and look up into where all the v-belts (or serpentine belt most likely in your case) are. You should see the fan blades where the fan mounts to is the "fan clutch". The fan clutch in turn bolts to the water pump.

Attached you'll see a fan clutch similar to what should be on your engine. Click image for larger version

Name:	typical-fan-clutch.jpg
Views:	86
Size:	31.5 KB
ID:	61595 You'll see four mounting holes on the upper round disk, thats where the fan clutch bolts to the water pump. The four mounting holes in the middle are where the fan bolts to the fan clutch.

When you're working on it you'll mostly be working blind, reaching down into the fan area. Won't be a fun task but its definitely doable. I doubt that you'll be able to remove the fan and fan clutch as a complete assembly because of the shrould on the radiator, of course you might get lucky!

My guess is you'll need to unbolt the fan from the fan clutch and just let the fan kind of hang on the fan clutch and then unbolt the fan clutch from the water pump. At that point you can pull the fan clutch away from the water pump and then slip the fan off of the fan clutch. I think once you get a good luck at the front of your engine you'll see what I'm talking about. Be real careful not to bang the fan against the radiator. You could damage the fins on the radiator that way.

Good luck!

Brad
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Old 12-15-2008, 03:09 PM   #16
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Hi all - I need to buy a new fan clutch for my 250 MH. Vin number is 1GBJP37N0M3301377. Most online stores seem to offer varying options for the P30 chassis, depending on the type of vehicle base e.g. Vin "W" base. For example:

Performance Parts Market - Auto Parts and Accessories Catalog - 1991 Chevrolet P30 Fan Clutch

Now, I always assumed my 250 was a "j" base (see VIN 4th digit) which is slightly smaller and lighter than the "k" base commonly seen in classic MHs. Anyhow, the upshot is I don't know which fan clutch to go for. I intend to ship one to the UK, so I need to be sure I get the right one. Can anyone offer any advice here? Most stores seem to offer 3 or 4 types for the different bases. Napa only offer one - perhaps I should go with them. Any advice greatly appreciated.

thanks
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Old 12-15-2008, 03:29 PM   #17
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I would go for the heavy-duty, thermostatically controlled fan clutch.
The non-thermo type is a "dumb" clutch, it doesn't know if the engine is hot or not. The thermostat will allow more fan movement when hot.
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Old 12-15-2008, 06:31 PM   #18
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Quote:
Originally Posted by Alumatube View Post
What can happen when a fan clutch engages inappropriately? I just had mine replaced on our Dakota, and it engages a lot when it should not (at starting, initial take-off, and taking off from a light or stop sign). It seems to work correctly otherwise. I have to go on an 1,800 mile trip starting tomorrow, the dealership did not order the part in to fix it (I took it back in enough time) because the foreman wanted a "second opinion" from the guy who did the work. He assured me that there would be no problem on my trip (What!?! He originally said he wasn't sure of what could be causing the problem so he wanted a second opinion!).

What else would make a fan clutch engage like this? And will it hurt my truck on a 3-day, 1,800-mile trip???

This makes me very nervous, but I really have no choice.

Susan
It is not uncommon for the clutch fan to engage when leaving a stop light. This is a result of heat building up in the engine compartment while stopped and that heat engaging the fan just as you start up.

Now there are a couple of reasons why a new clutch may do this when another one did not. The specification for these fans state that they may engage from 160 to 190 degrees F. If you new fan is at the lower end of this spec it will react sooner, more often.

Another thing that influences fan operation is the condition of the radiator. If the radiator is dirty inside it will not lower the water temperature as it should and the engine will tend to over heat. This over heating causes hotter air to flow past the radiator and contact the clutch causing the clutch to engage, but at a higher engine temperature.

If the radiator is clogged with bugs and other road dirt again the engine will tend to over heat but the clutch fan will not engage at a normal temperature.

I generally pressure wash the exterior of the radiator once a year and remove the radiator and have it cleaned internally ever couple of years.
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Old 12-15-2008, 06:36 PM   #19
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If yours has the top air pump, A/C compressor both in the way you'll find the only way to extract the fan clutch with schroud and radiator in place is to first remove the alternator creating a "hole" big enough for extraction. With alternator out of the way its much easier to get at the clutch mounting bolts/nuts also. I recently had a 6 month old clutch fail and really did not want to take everything from the grill back off again from a recent water pump change out.
My alt. is serpentine belt driven and R&R isn't bad at all from inside MH. Add this to everything in above posts and you should be good to go.
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Old 12-15-2008, 06:40 PM   #20
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Quote:
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Hi all - I need to buy a new fan clutch for my 250 MH.
Unless you can not turn the fan freely by hand while the engine is off, a lock clutch, I would suggest you have the radiator cleaned first. There is almost nothing in the clutch fan that can go bad. It is an oil fill dual fan converter with a bimetallic locking cam.
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