Possible way to test fan clutches

Still Kickin · 12-04-2016, 09:20 AM

Site team note: This post and subsequent responses was split from another thread, which it was unintentionally hijacking.

Not an owner but wanted to throw this out, easy way to test the fan clutch is; with motor off, manually spin the fan like a roulette wheel, it should only make between three or slightly more revolutions until back at rest. A truely bad clutch fan will spin freely, indicating the oil viscosity in the fan housing has failed.

tmmar · 12-04-2016, 10:17 AM

Quote:

Originally Posted by Still Kickin

Not an owner but wanted to throw this out, easy way to test the fan clutch is; with motor off, manually spin the fan like a roulette wheel, it should only make between three or slightly more revolutions until back at rest. A truely bad clutch fan will spin freely, indicating the oil viscosity in the fan housing has failed.

This is not easily done since the fan is completely enclosed in a shroud and you can only access as small portion of the blade from underneath the coach.

Iwannacamp · 12-04-2016, 02:45 PM

Most Cummins engines I see cycle the fan a lot. If you idle a lot there will be a/c issues till the engine reaches operating temps. They are either mechanically or electrically actuated temp control.

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Still Kickin · 12-05-2016, 08:33 AM

Quote:

Originally Posted by tmmar

This is not easily done since the fan is completely enclosed in a shroud and you can only access as small portion of the blade from underneath the coach.

Spin it from there then.

tmmar · 12-05-2016, 11:36 AM

Quote:

Originally Posted by Still Kickin

Spin it from there then.

Kickin,
I think that you should find a Berkshire and try to get to the fan and let us know how you make out spinning it. I think you will get a different perspective on how difficult it is to spin the fan that is completely encircled in a shroud.

Still Kickin · 12-05-2016, 11:50 AM

The information was instuctional only. If you think its your fan clutch, thats how you test it. If it's beyond a persons skill set, I respect that, in that case see your mechanic. Just sayin'

Phil57 · 12-05-2016, 11:56 AM

Quote:

Originally Posted by Still Kickin

The information was instuctional only. If you think its your fan clutch, thats how you test it. If it's beyond a persons skill set, I respect that, in that case see your mechanic. Just sayin'

Skill set really. This is not a pick up where you just open the hood. Even from the access hole in the back of the Moho it's a long stretch. Almost impossible to get to from the outside. The point is it's not that easy.
I'm also not convinced that this "test" will tell you if the fan clutch is bad. Most of the failures have been a failed mount. So this will tell you nothing.

Iwannacamp · 12-05-2016, 11:57 AM

I will say... I don't have a 340/360 IBS or whatever so my input may be useless and I see where the clutch can be crap, but I still say if I "spun" mine to see if it was bad... I would replace it most of the times I checked it unless the engine was at operating temperature... I do have a 6BT or whatever they call them now. JM semi-helpful information.

dan-nickie · 12-05-2016, 03:49 PM

Hold back boys. LOL

Still Kickin · 12-06-2016, 05:00 PM

Quote:

Originally Posted by Phil57

Skill set really. This is not a pick up where you just open the hood. Even from the access hole in the back of the Moho it's a long stretch. Almost impossible to get to from the outside. The point is it's not that easy.
I'm also not convinced that this "test" will tell you if the fan clutch is bad. Most of the failures have been a failed mount. So this will tell you nothing.

Suggest you re-read my post, I was offering my advice on specifics on how to check the viscosity of the clutch fan oil, which is a cause of some failures. As to my reference to "skill set" a master diesel mechanic would be a 10, a seamstress would be 0. The DIYer, falls somewhere inbetween.

Oh, the other way to check it, although just a little bit less exact, is start the engine, observe the fan spin at idle speed and while in sight, have someone turn the engine off. The fan should come to rest relatively quickly. Definitely in less than 5-8 full revolutions. What is puzzling is criticism for suggesting a way to determine clutch fan failure, due to oil viscosity issues. Just sayin'

Phil57 · 12-06-2016, 06:52 PM

Quote:

Originally Posted by Still Kickin

Suggest you re-read my post, I was offering my advice on specifics on how to check the viscosity of the clutch fan oil, which is a cause of some failures. As to my reference to "skill set" a master diesel mechanic would be a 10, a seamstress would be 0. The DIYer, falls somewhere inbetween.

Oh, the other way to check it, although just a little bit less exact, is start the engine, observe the fan spin at idle speed and while in sight, have someone turn the engine off. The fan should come to rest relatively quickly. Definitely in less than 5-8 full revolutions. What is puzzling is criticism for suggesting a way to determine clutch fan failure, due to oil viscosity issues. Just sayin'

Not sure it was criticism but its frustrating when the difference between P/U trucks and motor homes aren't respected. It's not a simple thing to get to the fan on a motorhome. In fact getting the access door open from the inside is a big job and even then depending on the models of Moho it will be a stretch to spin the fan. Getting to it from underneath is a job for skinny guys for sure. It's doable but not easy.
The clutch on a Moho is different than a P/U truck. The clutch is a oil filled electric controlled unit. As the speed and temperature change the speed of the fan changes. Yes the fan should not spin freely. It is actually hard to turn. Harder than any car I have dealt with. It also has nothing to do with the A/C as someone else suggested. The fan for the A/C is in front and not on the motor. The best way to test the fan is to pull the fuse or unplug the harness to the electric clutch. The fan when unplugged should go to full speed. This would indicate a functional clutch.
No disrespect intended here but also just because Ram trucks have a Cummins motor doesn't make them function the same.

Still Kickin · 12-06-2016, 07:01 PM

You waited till now to let the thread know this neat little tidbit .Still puzzled, but thanks for your contribution, readers of this thread thank you too.

Phil57 · 12-06-2016, 07:07 PM

Quote:

Originally Posted by Still Kickin

You waited till now to let the thread know this neat little tidbit .Still puzzled, but thanks for your contribution, readers of this thread thank you too.

I just learned that little tidbit. Most of the failures I have seen are due to a mount that fails due to broken bolts causing the fan/ clutch assembly going into the 5000$ radiator

Phil57 · 12-06-2016, 07:09 PM

Quote:

Originally Posted by dan-nickie

Hold back boys. LOL

I'm trying

Campin Cajun · 12-08-2016, 06:07 PM

Quote:

Originally Posted by Still Kickin

Site team note: This post and subsequent responses was split from another thread, which it was unintentionally hijacking.

Not an owner but wanted to throw this out, easy way to test the fan clutch is; with motor off, manually spin the fan like a roulette wheel, it should only make between three or slightly more revolutions until back at rest. A truely bad clutch fan will spin freely, indicating the oil viscosity in the fan housing has failed.

With how much force? This is a huge factor to leave out of your suggestion. Think of the Price is Right when a little old lady spins the wheel compared to a huge young man.

Still Kickin · 12-08-2016, 06:16 PM

I love that show. A good friend of mine won some nice stuff too. Yeah, spin it like you own it. Thats a good analogy. Otherwise, go to the alternative method and see how good you are having your head bob counting the revolutions as it spins to rest.

SidecarFlip · 01-02-2017, 09:02 PM

Quote:

Originally Posted by Superchief

Yes - Cause was belt tightener bearings freezing up and throwing the serpentine belt, which broke the connections to the fan clutch. When they replace the fan clutch, the Freightliner repair facility indicated that the fan clutch bearing was close to failing.

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I'm gonna jump in here. I don't own one but I've replaced a number of fan clutches in diesels and it's not that difficult. A frozen belt tensioner will cause issues like a thrown drive belt but are real easy for you to check and should be checked regularly like when you check the oil...

With the engine idling, look at the tensioner and see if it moves slightly as the belt revolves over it. It should. If it don't move at all, shut the engine off and insert a long screwdriver between the idler arm and the mounting bracket ans attempt to move it. If it don't move, it's frozen and needs replaced.

Fan clutches are easy but when you are paying a hundred per hour labor rates, costs add up fast. Glad I'm mechanically inclined.

kingwood390bh · 01-05-2017, 11:43 PM

On my 2010 390bh the clutch failed over several months. Engine temps would climb, the fan would eventually engage, and the temperature would fall. When functioning the fan moves a tremendous amount of air. When it finally failed, you could stand behind the coach and the air would be still. Access to the fan was gained by removing the floor in the mbr. My tech said it was no easy task removing and replacing it.
As an aside, I found that a box fan placed behind the radiator with a long extention cord was enough to get me to a mechanic.

SidecarFlip · 01-06-2017, 04:32 PM

Pretty much SOP on a pusher, remove the bedroom floor or pull the radiator and intercooler and ac condenser and do it that way. Some chassis ca be done from underneath but not FTLNR.

It's a job time wise but involves no special tools or jigs. The cost is in the hourly labor rate mostly. A reman clutch is under a hundred bicks.

You can actually so it in your driveway, no special skill required (othey than a lot of time.

Motor homes, especially diesel pushers are generally a royal PITA to work on, consequently owners get to pay big bucks for mundane tasks.

In our shop, which is a factory authorized Freightliner franchise, we have 2 labor rates. One rate (lower) for Freightliner trucks and another (higher) for Motorhomes with FTL chassis. Interesting, we are always backed up, winter and summer.

I just saw a Berkshire pulling in when I was leaving the shop yesterday....

jcowles3 · 01-06-2017, 07:49 PM

My rig had a big alignment problems that FL tried 3 times to fix at my cost.(still pissed) Local truck tire place fixed it. Back tires are the reference for front tires so my rear axel was off and in turn you could never align the rig. Why FL didn't look at rear is beyond me!

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