heard fan today 1st time

[daveshoe]

I heard the fan engage the first time today. I am curious how it works. It engages in hot weather after high speed runs and being idled down[stoplights & parking lots] . Once you get to speed, it shuts down. Also, after sitting for some time [mabe an hour] it will engage at startup. No problems with coolant temp as it stays at 185 or below on 98 degree days

mabe someone can tell me how it works and assure me all is well? Truck is 02 and is always loaded to 9500 Lbs

 

[csevers]

I bet it got your attention

The fan hubs on these trucks never are totally freewheeling there is some turning it is very normal to have more drive at start up till it sences temp to stay locked or free up I have had 3 other trucks before I had got one hot enough to get engine fan to come first time I thaught I had just blown something up sounds ok to me



motor on

 

[Lurch]

The fan clutch responds to underhood temp not coolant temp. On my black truck it would run at startup, every stop and go, etc. when the sun was warm.



Lurch

 

[dremelts]

As I understand it the fan has a viscous coupling in the hub. Temperature sensitive springs open/close ports that allow the fluid to engage the clutch or let it freewheel. That's about all I know about it - I've never actually dissected one. It DOES make a lot of noise though when it engages.

 

[illflem]

Dave's explanation is right on. Another thing I've noticed is that when it's very cold the oil in the viscous drive thickens and the fan doesn't freewheel as easily as it would in normal temps. Just when you need cooling the least it does more.

 

[Hummin Cummins]

Well that answered the question I was going to ask. I was hoping for some type of electronic sensor/switch that engages the fan. My Peterbilt has an on/auto switch for the fan. It's nice to put it "on" when cooling for shutdown. Its a Horton, though. I sat forever today just to hit 400* for shutdown with low 90's for Ambient air temps. To be able to lock up the fan at anytime would be nice. That and I guess the open filter underhood doesn't help much. Gotta get the Scotty system on.



Chris

 

[illflem]

Hortons sure are nice, too bad they're so expendsive. I read where Horton just sold their one millionth fan to UPS. That's saying a lot, UPS takes good care of their rigs, many are over 25 years old.