Chevy and GMC Duramax Diesel Forum - View Single Post - Clutch fan engagement
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post #4 of (permalink) Old 11-06-2018, 04:44 PM
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Join Date: Oct 2009
Location: Jax, FL
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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.

09 GMC SLT Dually
Steel Gray Metallic
All options except sunroof

Mods so far:

Alcoa 19.5s with Michelin XZE, Centramatics,Tow Mirrors, Chrome Grill Overlay, Rear underseat storage, Mudflaps all corners, 20% Window tint, 6" Oval Steps, B&W Turnover Hitch, B&W Companion Hitch, Sulastics, GM Campaign #PIT3009J, Wireless Console Charging, Bilstein 5100s, Raptor 3602RL
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