Clutch Fan Question.

[SHOPMAN426]

I would like to know if when the clutch fan kicks in, is it running because of the heat in the tubo? Over the Thanksgiving week I pulled our new fifth wheel down to San Diego from Portland. On long hills the fan would engage. It would run a predetermind time. During this time I saw no change in the engine temp. gauge. Going up the grapevine the truck was in third at about 45 mph. The fan engaged three times and the interval seem to be the same for how long it stayed engaged. Any help from you guys that haul heavy loads. BTW, the fifth wheel weighs in around 9000 lbs.

Thanks, SHOPMAN426.
Mike. :confused: :confused:

[DmaxMaverick]

Operation of your fan sounds completely normal.

The clutch responds ONLY to the temp. of the air passing through the radiator (except on a cold start, due to cold fluid in the clutch). The reason it seems to run for a predetermined time is the efficiency of the cooling system of the engine, which is very good. It's only a coincidence that the timing seems the same. Your engine temp gage may or may not indicate any change. Some do, some don't, and it depends on just how hot it gets at the time the clutch engages. The Duramax has 2 thermostats in parallel that open at different temps. During colder ambient temps, the secondary stat may never open, even under heavy load. The gage, from what I've observed, won't move any detectible amount at the time only one stat opens.

Don't worry. It's normal.

[SHOPMAN426]

This is a little off the topic, but whats the deal with Auto's With Trailers speed limit is 55, while the speed limit is 70 for non towing. I had a CHP pull up along side me and give me the five five hand sign. I guess thats better than getting a ticket for going 62 mph.

SHOPMAN426,
Mike. :eek: :eek: :eek:

[SHOPMAN426]

Wow! It's amazing what a guy can learn here. Thanks a whole lot for that indepth explanation.

Thanks, Shopman426.
Mike.

[DmaxMaverick]

Yup. The speed limits are a bit kooky. This state has to get a lot less blue before that (along with several other really stupid regulations) will change.

Boxer and Frankenstein (did I spell that right?) sure keep this republik upside down.

[navajochief]

Had my '04 LLY do the same thing. I was only towing under 6,000lbs. The fan clutch would come on like a crop duster. I'm in litigation now attempting to "lemon" the truck. As far as the turbo goes, I recently took my truck in to the dealer just two weeks ago because the "check engine" came on. Once it was scanned, some ten page report was given pinpointing turbo problems. It turns out I have a bad ECM. It was running my turbo at 100% all the time. Since buying the truck back in 2/04, I've had that fan clutch running even when I wasn't loaded. The truck never overheated, but the fan would never kick off sometimes. I could understand if I were towing with a heavy load up a 6% grade in 110 degree heat for an extended period of time, but the fan would kick on even when I would drive around town or on short trip to a neighboring town, on flat ground. Good luck. I think the '05 have electrical fans. Don't quote me on that.

[Kennedy]

Originally posted by SHOPMAN426:
This is a little off the topic, but whats the deal with Auto's With Trailers speed limit is 55, while the speed limit is 70 for non towing. I had a CHP pull up along side me and give me the five five hand sign. I guess thats better than getting a ticket for going 62 mph.

SHOPMAN426,
Mike. :eek: :eek: :eek: Trying to keep people towing from rear ending people and losing control. 55mph is a bunch safer for stopping, sway, and handling.


Fan clutch operation sounds normal.

[SHOPMAN426]

That is true, however I have people cut in front of me no matter how fast or how slow I am going. The problem I see is, if I am going 55 down the freeway and I come up on a slower vehicle, its hard to move over to pass while everybody else is blazing by. Then I end up slowing down and waiting for an opening. The minut you put on the blinker everybody bunches up to lock you out. I'm not saying that I want to run 70 but 60, 62 would help. In Oregon the law is 65 for cars and light trucks,(trailers or not) Big rigs run 60. Oregon has a rule of 5 mph difference between vehicle speeds. This is why our limits are not up to 70 mph at this time.

Just my thoughts, Shopman426.
Mike.

[More Power]

All 2001-2005 Duramax powered 2500HD/3500 trucks have a belt driven viscous fan-clutch that utilizes a bi-metallic coil to control engagement.

The light-duty gassers got an electric fan-clutch in '05.

Accessories like grille inserts and brush guards can affect airflow through the radiator, which could affect the temperature seen by the bi-metallic coil, which in-turn could determine how often it engages the fan.

MP