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dhwhite 06-30-2005, 05:42 PM I have an '05 GMC 3500 dually with the duramax diesel engine. Sometimes, when I am towing a heavy load in hot weather, the engine makes a high-pitched roaring noise. This may continue for several minutes. The engine rpms apparently do not increase during this period. What is this noise? Is it normal or do I have a problem? Billman 06-30-2005, 05:45 PM Probably your fan kicking in... McRat 06-30-2005, 05:46 PM Normal. It is the engine fan. Irritating as heck though. dhwhite 06-30-2005, 05:53 PM Thanks McRat, yes it is irritating. Normal. It is the engine fan. Irritating as heck though. lakingslayer 06-30-2005, 06:56 PM Thanks McRat, yes it is irritating. A lot less irritating than overheating because it didn't do it's job. DURAtotheMAX 06-30-2005, 07:41 PM Mine sometimes comes on for no reason whatsoever as I pull out of the driveway in the morning... Actually ive found that if you kinda "deliberatly" let off the accelerator and then step on it again, my fan turns off. I dunno if my fan clutch "sticks" and that unsticks it, or its just a pure coincedence that it shuts off then because the computer/t-stat realizes that the truck has been running for all of 2 minutes and there is no need for the fan. Then again it hardly EVER comes on while driving, even on 95* days when the truck has been running for hours. hmmm... ---Ben Jamie218 06-30-2005, 08:01 PM Completely normal. Called the dealer about this issue, top mechanic said it before I could get the word out of my mouth. He said it happens on his 8.1 that he has. Told him that it kinda sounds like a jet airliner under the truck. He said that the fan clutch is doing its job. Nothing to make it quiet, hell of a fan. Temps never run hotter than if I was not towing my 5'er. Just started when towing in the 75 and above air temps. A/C cranking, feels like a freezer in the truck, so it is doing its job. | ||