NEED HELP Fan Clutch Troubleshooting

Fastlane

Original poster
Member
Feb 2, 2015
6
Hi All,

Want to preface this by saying that I have looked through many threads regarding the electro-viscous fan clutch, and I'm still stumped.

The problem started on a long road trip, where it threw a fan speed too high code. Since the road trip, the fan would not seem to change speed, nor was it fully engaged. I also hooked a snap-on scan tool to it, and when commanding it to change speeds, it would not do so. The engine would be very rough at idle and vibrate the whole vehicle, as if the fan wasn't fully disengaging.

I replaced the clutch recently, with the AcDelco/Behr OEM replacement from amazon, and now it's even worse. The fan is stuck fully engage (jet engine sounding) at cold startup, and disengages after 2500 rpm (revved at idle or driving), then seems to operate as "unlocked." I can stop the fan by hand at idle, and when revving engine, it does not start to pull/tug as if it was commanding a lockup. I have yet to test this while commanding lockup with a scan tool.

I have checked the #20 fuse and relay, and have swapped the two solid state relays in the underhood engine block with no change.

While I have found a few test procedures to try, none are very clear or seem to apply to my situation completely. If anyone can offer any advice on how to track down the problem, I would greatly appreciate it. Thank you!

2005 GMC Envoy 4.2L
 

Blckshdw

Moderator
Nov 20, 2011
10,665
Tampa Bay Area, FL
It sounds like your new clutch is operating normally. It's not uncommon to get the jet engine roar sound at first on a cold start, and then it fades away after a minute. I used to have a pic from HP Tuners that shows the chart of commanded fan clutch lockup percentage vs engine coolant temp, but can't find it. In short, it's not really asked to do much of anything until things get over 210.

Does your fan roar EVERY time you start the truck? Or only from cold starts?
 

Fastlane

Original poster
Member
Feb 2, 2015
6
It sounds like your new clutch is operating normally. It's not uncommon to get the jet engine roar sound at first on a cold start, and then it fades away after a minute. I used to have a pic from HP Tuners that shows the chart of commanded fan clutch lockup percentage vs engine coolant temp, but can't find it. In short, it's not really asked to do much of anything until things get over 210.

Does your fan roar EVERY time you start the truck? Or only from cold starts?

Hi Blckshdw,

The reason it bothers me so much is because the fan I replaced did not make the roaring noise at startup. And with the replacement, the noise seems excessive, as if the desired speed is less than the actual speed.

If the fan is not matching the desired speed at idle, why would this be?

If it does not match the desired speed while in operation, I believe this would still indicate a problem, right?

The idle is also rough, which I believe is due to the fan being locked up, as the idle was perfectly smooth before the problems occurred. What are your thoughts on this?

Thanks for your help!
 

Blckshdw

Moderator
Nov 20, 2011
10,665
Tampa Bay Area, FL
Due to residual friction in the clutch from the nut spinning with the water pump, the fan will always spin when the engine is on. You'll get the roar when the fluid inside the clutch has pooled in the bottom. Here's a post and video that was posted a while back that might be helpful. My guess is, just due to the way your new clutch is built internally, the fluid pools easier in the bottom of the new clutch than it did with the old one.

Welcome to the Nation!

It's normal operation.
Reason for fan at startup?
Basically, as the silicone fluid will pool into the clutch, it will be engaged until the fluid heats up and returns to the reservoir. This video shows how it works (electro-viscous is basically the same except electrically instead of thermally controlled)

Although they don't mention it, the fluid will leak down into the shear plate overnight. Until it gets back into the reservoir, it will be engaged.
 

Eric04

Member
Dec 3, 2014
392
West Michigan
Taking a stab in another direction, your fan code, while correlative, may not be causative regarding your idle. The clutch shares a reference signal with the throttle body and the acceleration pedal position(APP) sensor. It's not uncommon to have a fault in one trigger a code for one of the others. When was your throttle body last cleaned? Was the relearn procedure done after(power disconnected for 30 minutes)?

I'm going in this direction because I too think your new fan clutch is operating correctly and your old one was probably long dead and just along for the ride. Given that the code popped when your idle problems began I think it's worth checking the state of the throttle body at this point.
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
:iagree::iagree::iagree:

And maybe the reason the new clutch is so stiff on startup and takes a while to slow down again is because it has new fluid, which might be thicker than old fluid. It might loosen up over time. I have a thermal clutch in the Saab and it still acts the same way.

If you disconnected the battery at all, then it will bring on the idle issue if you also don't clean the throttle body. Just coincidence.
 
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Fastlane

Original poster
Member
Feb 2, 2015
6
Hey all,

Finally was able to dig back into the vehicle and use the fancy scanner. The desired fan speed and actual fan speed are still nowhere close to being similar, whether at idle or RPM. (See attached pics and note vehicle rpm in background) :Banghead::sadcry:

With the scanner, I was able to command it from 0%-100% lockup, but the scanner would not show the desired/actual speeds, but there was a audible difference of it spinning faster when commanded to 100%.

Throttle body was fully cleaned prior to these readings, and the battery was disconnected for 30+ mins.

Idle is still rough, which I still believe is due to the fan spinning faster than it should. As the rough idle started the same time the fan problem started. 🤷‍♂️

When the fan clutch is unplugged, it still roars at idle up to ~1500RPM, then slows when it unlocks.

What additional tests can I do to help isolate the problem? Thanks.
 

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Blckshdw

Moderator
Nov 20, 2011
10,665
Tampa Bay Area, FL
I don't think you can equate engine RPMs to fan RPMs, since the fan is spun off the water pump pulley, not the crank. Think of it like a bicycle with different sized sprockets between the pedals and the rear wheel allowing the wheel to spin much faster than you're pedaling.

To rule out fan overspeed being the culprit, you could disconnect the fan clutch from the water pump pulley, and run the engine for a little bit to see if the idle smooths out like you're expecting. If it does, then a new fan clutch is in your future. If not, then we'll have to divert our attention elsewhere.
 
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