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Old 09-24-2020, 06:41 PM   #1
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8.1 Workhorse Cooling Fan Questions

I have just come off hopefully the final fix for having to replace too many plug wires on my 8.1 leading to less than full power, misfires, and poor fuel economy. The fourth mechanic in a three year ongoing problem diagnosed leaking exhaust gasses from the manifold gasket which was lately frying the wires in less than 1000 miles. Fixing that plus some plug wire heat sleeves hopefully will get me more life out of the wires and better performance. I understand these engines have a tendency to fry wires regardless. But thatís another story.

So the HR Admiral comes back from that repair engine running great and full power as it has been when the wires have been good. However it seems a lot louder than before. My wife notices it too. I first suspected it was the transmission not finding its final gear. These Workhorse chassis have a GM Hydra-Matic 4L80-E 4-speed which is an Allison. I had it looked at and they checked the fluid, found no codes and it shifting normally. It almost sounds like at 75 mph it needs to drop into overdrive except it is already in fourth and there is no over drive. Itís running about 22-2300 at 65. So I think the tranny is operating normally and isnít the cause of high rpms and attendant noise

On to the cooling fan. There is a lot of chatter online about the fan being loud when it kicks in. In the past in the Southwest, not in the summer when I am smart enough to not be there, but when temps are in the 80ís and 90ís the fan would cycle on and off every few minutes with an attendant loud roaring sound. As best as a I can recall similar to what I hear more continuously now at freeway speeds.

Now to the questions. Are the fans running continuously in error causing the higher noise? Canít tell. At both start up and when I came off the road today into service plazas and rest stops and immediately popped the hood, the fans were idle. Never heard them cycling on and off like I have heard in the past. I donít know how to verify the fans correct operation. How would you do that? I note there is no overheat problem. I was running in temps in the 60ís today. Maybe cool enough the fans didnít need to come on. Donít know. The temp gauge is right in the middle where it always is. I ran 8 hours today three hours of which were in some pretty good hills in Pennsylvania. No overheating going on.

How do the fans work? Temp sensor on the block, a relay, some kind of a electronic clutch control to turn them on. I think they are electric not driven by the serpentine belt. Anything o can check myself?

Just to be clear, I believe the engine is louder than normal. Checked transmission, now looking into the fans, perhaps it is something else.

Iím hoping this is something I can figure out. Itís been an expensive summer for that engine. Any ideas would be helpful.
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Old 09-24-2020, 07:21 PM   #2
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What year is it?
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Old 09-24-2020, 07:25 PM   #3
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Just a clarification:


You said: "Workhorse chassis have a GM Hydra-Matic 4L80-E 4-speed which is an Allison"


No, the 4L80 is a GM, not Allison transmission. Allison transmissions are the 1000, 2000, 2500, 3000, 4000....


With the W chassis, you should have the Allison 1000. Depending on year, likely a 5 speed.
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Old 09-24-2020, 07:36 PM   #4
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The 8.1 is known to blow exhaust manifold gaskets. I just had to replace one in my 8.1. Check along the back side of the manifold for a noise and you can feel the air coming out. If you raise the front with the levelers you can access the area from the front wheel well and it can be changed after removing the wheel.

The fans cycle on and off as needed and mine does it even if you pull a slight grade.
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Old 09-24-2020, 08:25 PM   #5
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The fan clutch is a thermal expansion bimetal coil that allows a viscous fluid to flow into the clutch assembly, their usual failure mode is free spin on the shaft and not blow air, though they can also lock up all the time.


A few things to check:


Unbolt the air conditioner condenser and see if the front of the radiator is clogged with debris. These stacked radiator assemblies are bad about getting clogged where the 2 sandwich together, and look ok from the front and back. The consdenser must be partly removed to see the gunk, then you can hose it out with low pressure water.


Bite the bullet and buy the good Extreme Magnum spark plug wires from Ultra RV Products, and be done with it, they are expensive but they don't tend to burn out like lesser wires.


p.s. the P series chassis with the 8.1L have the 4L80 or 4L85E 4 speed transmissions, the W series has the 5 or 6 speed Allison transmissions
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Old 09-25-2020, 07:08 AM   #6
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I had a leak on my driverís side exhaust manifold, replaced the stock studs and nuts with ARP stainless. They stay tight, donít rust and are very high quality parts that donít really cost more than the stock GM parts. I agree with the Ultra RV Magnum wires. I put them on and never had a problem again. The fan clutch will go out with age, try turning it and see what happens. Should have some resistance to turning. Also, there are rubber seals on each side of the radiator shroud to keep air flowing properly for cooling. These seals are only clipped in place and have a propensity to fall out.
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Old 09-25-2020, 12:36 PM   #7
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Update

There was a typo in my post. The Transmission on my Holiday Rambler Admiral is an Allison 4L85 -E per the build sheet for the motor home. To answer another question it is a 2004 motor home.
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Old 09-25-2020, 01:00 PM   #8
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The 4L85E is NOT made by Allison , it is made by GM, the 4L85E was introduced in 2003 as a beefed up version of the 4L80E, externally the later (post 1998?) 4L80E and the 4L85E look identical
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Old 09-25-2020, 06:02 PM   #9
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The electric fans in front of the radiator do not make enough noise at road speed to be heard. If you are hearing a loud roaring type noise, suspect a faulty viscous fan coupling, or restricted air flow thru radiator. As for the dash temperature gauge reading only a bit above half way, the gauge is very inaccurate, to the point of being worthless in pointing out the operating temperature of the engine. Good advice on cleaning radiator fins, and checking operation of viscous coupling of engine fan.
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Old 09-27-2020, 12:44 PM   #10
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If I read the OP's post right he said it was making more noise after he had had it worked on. A similar situation happened to me. The mechanic said it seemed to make a lot of engine noise when he test drove. After I looked at it he had not replaced the dog house properly. Once I replaced it correctly, wala, the noise went away. It was not extremely noticeable that it was not on right.
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Old 10-08-2020, 05:52 PM   #11
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Quote:
Originally Posted by Isaac-1 View Post
The 4L85E is NOT made by Allison , it is made by GM, the 4L85E was introduced in 2003 as a beefed up version of the 4L80E, externally the later (post 1998?) 4L80E and the 4L85E look identical
Interestingly enough, my build sheet says 4L80 and mine is, in-fact a 4L85.

You can tell the difference by the cooling lines on the trans. If they are right next to each other, then it's a 80. If they are separated by about 9 inches, it's an 85.
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Old 10-08-2020, 06:06 PM   #12
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You are wrong on that, the later 4L80 built after about 1999 also had the wide cooling lines. Externally a late 4L80E and and a 4L85E are identical, the difference is internal in I think the 4th gear assembly.
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Old 10-11-2020, 12:39 PM   #13
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It sounds like the water pump clutch fan ,when they go bad it makes the big 5 blade fan run all the time ,I replace mine they have me the wrong so check the number on your old one ,try autozone ,also take out alternator & bracket to make it easier, be carefully not to hit radiator with the fan .good luck
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Old 10-11-2020, 01:28 PM   #14
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Just a note here the 8.1L P32 Workhorse fan clutch is a Workhorse only item, there are no aftermarket ones that match up, unlike the 7.4L P32. I bought mine from Ultra-RV products a couple of years ago, pricey, but I could not find it cheaper anywhere else. Also they can fail both ways, locked up and spin all the time, or not spin when they should, or not come on until higher temperature than they should.
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