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Old 08-14-2017, 10:25 PM   #1
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8.1L GM class A engine whirling sound

I don't know how else to describe the sound when the RPM's get up there wether it be pulling a grade or engine braking.

My question is simple. Is there a particular component making the whirling sound? Engine Fan, Air Intake, etc...

My experience with regular autos and trucks has been one of the above (air intake or non electric engine fan).
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Old 08-15-2017, 12:43 AM   #2
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When climbing a grade and the engine starts to heat up you engine fan will engage and create a really loud roaring noise until the engine cools down.

When I climb mountains I keep my RPMs at about 3600 rpm as that's about where the maximum torque is produced.
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Old 08-15-2017, 12:55 AM   #3
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Yep, just like Arch said. The noise is coming from a large fan connected to the front of the engine. When the thermostatic coupling in the fans clutch reaches a certain temperature the clutch begins to engage the fan and draw air through the radiator. If the coupling exceeds that temperature the clutch locks up even tighter and the fan makes more noise.

If you have the ability to monitor the actual coolant temperature you will notice the clutch engages the fan at about 205f on the coolant temp. If the coolant temp reaches about 212f the clutch will be fully engaged. The clutch will disengage once the engine coolant is back down to an acceptable level which is typically 198f or lower.

The clutch does not engage and disengage the fan based on coolant temperature. It engages and disengages based on the temperature of the thermostatic coupling device inside the clutch fan mechanism. There is some magic going on inside the clutch fan and this is basically how it works.
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Old 08-15-2017, 01:04 AM   #4
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Here is a little video describing how a typical clutch fan works.

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Old 08-15-2017, 01:10 AM   #5
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Here is a viscous coupled fan clutch. It's a little more sophisticated than the old school style fan clutch in the first video. I believe this is very similar to the type of fan clutch found on 8.1 Vortec engines.

Now you know everything about a Fan Clutch.

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Old 08-15-2017, 07:37 AM   #6
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You are a star for finding and posting that "How does a viscous fan clutch work?" video. Great explanation! And it also confirms that the coupling acts on air temperature and also, I assume, engine block temperature as conducted to it. That video should go in the Workhorse chassis forum in my opinion for those searching this issue in the future.
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Old 08-15-2017, 07:56 AM   #7
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Ok. Makes sense. So next question. Could you convert this to an electric fan design? Wouldn't that quiet it down significantly along with other benefits?
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Old 08-15-2017, 08:22 AM   #8
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I had a similar whiring sound in our 8.1L engine. It was the fan belt tensioner that was the problem. I replaced it and the problem was gone.

The fan belt tensioner is not hard to replace, but does take some planning, tools and leverage.

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Old 08-15-2017, 08:23 AM   #9
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When the fan isn't runing I can hear the P/S pump.
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Old 08-15-2017, 08:37 AM   #10
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Can the thermostatic coupling be replaced?

Quote:
Originally Posted by AKIQPilot View Post
Yep, just like Arch said. The noise is coming from a large fan connected to the front of the engine. When the thermostatic coupling in the fans clutch reaches a certain temperature the clutch begins to engage the fan and draw air through the radiator. If the coupling exceeds that temperature the clutch locks up even tighter and the fan makes more noise.

If you have the ability to monitor the actual coolant temperature you will notice the clutch engages the fan at about 205f on the coolant temp. If the coolant temp reaches about 212f the clutch will be fully engaged. The clutch will disengage once the engine coolant is back down to an acceptable level which is typically 198f or lower.

The clutch does not engage and disengage the fan based on coolant temperature. It engages and disengages based on the temperature of the thermostatic coupling device inside the clutch fan mechanism. There is some magic going on inside the clutch fan and this is basically how it works.
My fan engages way too much, even at 180 degrees. Can the coupling device be replaced or do I have to buy a new fan?
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Old 08-15-2017, 09:30 AM   #11
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Quote:
Originally Posted by GEM1N1 View Post
Ok. Makes sense. So next question. Could you convert this to an electric fan design? Wouldn't that quiet it down significantly along with other benefits?
I'm sure it's possible to convert to a couple of high cfm electric fans but chances are they would not be as efficient as the OEM clutch fan and on really hot days with long steep pulls they may not provide enough flow through the radiator to keep the engine cool. The reason the fan is making so much noise is because it's pulling massive amount of air through the radiator.

If it's the fan noise that's bothering you then you could spend a couple of hundred dollars and install a dynamic sound deadening liner to the under side of the dog house and the under side of the cabin below the driver and passenger seats. This will reduce the noise and heat dramatically and make the drivers area much cooler as an added benefit.

Here is one source. Dynamat Xtreme Bulk Pack 10455

Would look similar to this except under the doghouse and cab.



Quote:
Originally Posted by KOPQ View Post
I had a similar whiring sound in our 8.1L engine. It was the fan belt tensioner that was the problem. I replaced it and the problem was gone.

The fan belt tensioner is not hard to replace, but does take some planning, tools and leverage.

Dave & Sue Perrin
2004 Winnebago Brave 34D w/ 8.1L Workhorse engine
Yep. Two distinctly different sounds but both can be just as annoying.

Quote:
Originally Posted by speed racer View Post
When the fan isn't runing I can hear the P/S pump.
I can too on our Itasca. I used to worry about it when the coach had 7000 miles on it but now at well over 40k it's just something I live with. It quiets down after things warm up.

Quote:
Originally Posted by renorich View Post
My fan engages way too much, even at 180 degrees. Can the coupling device be replaced or do I have to buy a new fan?
The fan clutch can be replaced fairly easily. It's available from several sources including one of the sponsors on this forum. The beauty of using this sponsor is they run your Coaches VIN number so you know you are getting the exact part you need and you are getting a brand new OEM fan clutch. It may be a little more expensive than a cheap rebuilt unit from ORileys but it will likely be the last clutch fan you buy for that motorhome.

https://www.ultrarvproducts.com/Work...Clutch-Fan-Asm
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Old 08-15-2017, 04:29 PM   #12
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Quote:
Originally Posted by GEM1N1 View Post
Ok. Makes sense. So next question. Could you convert this to an electric fan design? Wouldn't that quiet it down significantly along with other benefits?
Don't think so... Our last coach had the two electric fans in front of the cooling pack. When the engine temperature hit the computer's mark, those puppies kicked in and were very noisy. They do move a lot of air.
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