Chevy and GMC Duramax Diesel Forum

Chevy and GMC Duramax Diesel Forum (
-   04.5-05 LLY Duramax Powertrain (
-   -   Clutch fan engagement (

Newman1415 09-17-2018 08:36 AM

Clutch fan engagement
I noticed yesterday while pulling about 11,000 lbs up a grade the engine got hot, very hot. The clutch fan never engaged where as it used to come on at a certain temp I believe. Would there be a fuse? Or something mechanically wrong with it? To think of it now I never hear it anymore at all. Sometimes on a cold engine it would run until the engine warmed up a bit too. Haven’t heard it in years.

Hook'em_Horns! 09-17-2018 08:50 AM

Look into opening up and cleaning your cooling stack out front.
Bugs, grass, debris can collect between the coils over time, restricting the flow of air to the fan clutch....which results in no heat detected and no full lock to cool down.

Peruse thru this thread, lots of pics of what kind of buildup you can find.
Spraying thru the grille at the car wash, won't do it. It needs to be opened up some to properly clean.

Newman1415 11-06-2018 01:05 PM

So aside from cleaning the stack. Which I haven’t, I have heard these fans can sometimes just fail and need to be replaced. That true? I’ll be doing a stack clean out soon just don’t have time....I also put new thermostats in last year in hopes to earn up the engine in these colder days. I currently have the new thermostats and a winter grille bra cover on driving highway speeds for 20 mins in 53 degree Fahrenheit and it barely gets above 185 degrees...what’s going on here? Figured it would be over heating in this weather with a bra

JimmyD 11-06-2018 04:44 PM

In addition to what Hook has stated, here is my experience with the fan clutch, pulling heavy up and down mountains/grades. My truck is an LMM but yours should react similarly. My 5vr weighs 14k.

As I pull up the grade, my engine temp will gradually rise to around 230. When it gets to 230 the fan clutch engages and trust me you will know when it engages as it sounds almost like the intake of a jet engine under your hood. My fan clutch remains engaged until the engine temp returns to 190/200. This cycle repeats itself until I get out of the mountains/grades. I rarely have the fan clutch engage when towing on flat ground, regardless of outside temperature. All of these examples above are with the ambient temperature 75 to 80 degrees F.

Hope this helps.

Newman1415 11-07-2018 05:06 AM

Yea so back years ago when I first got the trucknit made the morning sickness sound when cold, and when towing a couple fines up grades it also came on.

Thus past summer I was towing and it was over 230, truck warned engine coolant was hot, I let off and then it warned me engine over heated...I haven’t heard morning sickness fan sound in years

JimmyD 11-07-2018 05:34 AM

Sounds like a cooling stack cleaning and perhaps new fan clutch may be in order.

CA88 06-07-2019 05:32 AM

How long does it take to clean the cooling stack and flip the tranny cooler? Bout to make a road trip to Colorado haulin a trailer. Gonna replace fan clutch too.

Hook'em_Horns! 06-07-2019 07:14 AM

I think the only gain in moving the cooler, is when you've got an aftermarket bumper that blocks the air flow to the coil. Otherwise, the stock air slot is sufficient.

CA88 06-07-2019 01:24 PM

Yes hook I have an aftermarket full replacement bumper. The brand is thunderstruck

Hook'em_Horns! 06-07-2019 01:43 PM

In my case.....keeping the stock bumper and air bags plugged in....keeps me out of 'Oops!' trouble with idiots on the road. :teehee

But I often dream of a MadMax bumper mod....for the "blip, you hear somethin'?" marx

All times are GMT -7. The time now is 08:44 PM.

Powered by vBulletin® Copyright ©2000 - 2020, vBulletin Solutions, Inc.
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
User Alert System provided by Advanced User Tagging (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.

For the best viewing experience please update your browser to Google Chrome