Lately, every morning on a cold start my fan clutch kicks in and roars until I'm a good 2-3 blocks from home. Kind of hard to not wake the neighbors! On another note, I pulled my 7,000 pound fifth wheel last weekend in 95 degree midwest heat. Both the engine and transmission ran within normal operating range, but while driving the interstate at 65 MPH on cruise control, the fan clutch kicked in and would stay engaged for a mile or two before quieting back down. The temp gauges never seemed to move......Sound normal, or do I need to go see the dealer? Thanks for your input!

Smurph

Mine is on in the am for a short while, I think it is normal. There were a few comments about that last year.

I believe this makes the engine warm up faster and it might not be the fan just not going up in the gears. Doesn't the manual tell this? chevman

Does it on mine sometimes as well as on the 97 and 01 gassers I had. Doesn't seem to be a problem.

Perfectly normal. When shut down, the fluid drains into the clutch chamber and transfers torque until it can be pumped back out (by the differential rotation). Then it stays out until the thermostatic valve lets it back in when the discharge air gets hot enough.

The operation you hear on the road is also normal and good. The fan should start clutching up before the engine gets too hot. That's the whole point. When you don't hear it, and the temperature rises, it's time for a new clutch.

There is a heck of a fan connected to that thing. It does roar a bit when the fan gets spun fast by the clutch.

You should go out and kiss that fan clutch. There are people here that find out theirs don't work when they are pulling a grade with a 5th wheel and overheat.

Does GM have a new fan clutch part number due to the overheating problems other DMax owners have??? I rarely hear mine, even with the A/C on.

Fan stays on when the engine is cold, untill you rev it past 1800 rpm.

Same here. Lots of noise until I hit about 1600 RPM and kicks in and out when the engine is in normal op temp. Its doing its job.

Does GM have a new fan clutch part number due to the overheating problems other DMax owners have??? I rarely hear mine, even with the A/C on.
GM doesn't have a new clutch P/N. They only come on when your engine reaches about 205 to 210deg while driving when they operate correcty.

Anyone have an opinion on replacing the stock fan clutch with something like the old style flex fan? In other words, a hard mount that just spins the fan at engine RPM.

The fan clutch does not operate in only "on" or "off" modes - it gradually engages as the heat load increases. That's the reason your A/C cools at low speeds without any unusual fan noise - the clutch is compensating as needed for the increased heat load. You may also hear the fan run at full lock up for a short time after you have shut a hot engine down and then started back up a few minutes later - this is due to the underhood temps "heat soaking" the clutch. Sounds like your fan is working just the way it was designed.

2004 2500HD LLY CC SB

The only problem I see with a flex fan would be it is designed to pull air mostly at lower speeds (lower rpm) which was fine for a gasser with a thin stack to cool, but our setup relies heavily on the fan to cause a pressure drop that forces air to rush across the stack and cool the condenser, intercooler, and radiator.

I wouldn't want to hit a steep hill with a heavy load, cause a downshift (higher rpm and boost, overall thermal load increase) along with a speed decrease and have my flex fan flattening out on me and pulling less air. The flex fan definitely relies on vehicle speed providing enough airflow through the stack but in our case the stack is far too restrictive.

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