I6 fan operation

[signalnc]

Can anyone tell me how the fan is supposed to operate on an 4.2 I6? when I start my wifes 2003 TB it sounds like an airplane, then it goes away after a few minutes of warming up , or it goes away after you start driving. Is that normal? thanks.
I just don't quite understand how it is supposed to work. I'm thinking it has a clutch in there and the computer tells it to engage to produce more air flow.

 

[The_Roadie]

That's sort of normal operation, but as the pre-2005 fan clutches age, they can get noisier and noisier until they stay engaged all the time and sound like an F16 on afterburner. Many, many discussions about replacing them and getting a PCM update from the dealer to fix the reliability issue and improve AC operation on start-up in hot weather.

For more reading, trailvoy had the definitive threads:

Fan clutch 101 - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum
service bulletin# 060602003 - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum

And here's a couple of useful documents:

<dead link>[PDF]http://www.roadie.org/TechlinkEVClutch.pdf[/PDF]
Another source: http://www.norcal-cobras.com/GTM/gm-tech-link/7_02_e.pdf

<dead link>[PDF]http://www.roadie.org/fanclutchalldata.pdf[/PDF]

 

[Wooluf1952]

Can anyone tell me how the fan is supposed to operate on an 4.2 I6? when I start my wifes 2003 TB it sounds like an airplane, then it goes away after a few minutes of warming up , or it goes away after you start driving. Is that normal? thanks. I just don't quite understand how it is supposed to work. I'm thinking it has a clutch in there and the computer tells it to engage to produce more air flow.

The sound at start-up is not unusual. As long as it goes away, it's fine. Also, yes, that's how the fan clutch works.

Damn, I knew I should not have gone for coffee.
Nice new info, Roadie.

 

[signalnc]

thanks for the info. I'll read up on it.