Diesel Place banner

1 - 16 of 16 Posts

·
Registered
Joined
·
89 Posts
Discussion Starter #1
I just noticed this today. Not sure if it has always done it, but you can hear the fan running. It has kicked in a few times just after pulling it out of the warm garage. Actually it has kicked on a few time out of the blue. Maybe a cause for my low fuel milage.
 

·
Registered
Joined
·
263 Posts
Thought the fan was only driven by the drive belt...no?
 

·
Registered
Joined
·
89 Posts
Discussion Starter #3
It is belt driven, but actuates probably by a thermo clutch. Just weird that it is spinning fast enough at idle that you can hear it running.
 

·
Registered
Joined
·
2,473 Posts
When i start my truck up the fan will sometimes stay on for a period of time. Loud enough to hear at idle. And yes it is activated by a thermo clutch, but always comes on when first starting the truck, i find most times it shuts off pretty quick but sometimes i will go a mile before it will shut off
 

·
Registered
Joined
·
265 Posts
I live in SoCal and park my truck in my garage. If I let my truck idle for more than a minute or two in the morning before driving the fan will come on for a couple of blocks. It is very loud and very irritating! I was going to post on here to see if it was happening to anyone else. Specialagent beat me to it.:) It has never come on any other time.

Rick
 

·
Registered
Joined
·
89 Posts
Discussion Starter #6
I live in Alaska, it's winter, WTF is the fan coming on for?:wtf1:
 

·
Registered
Joined
·
120 Posts
Often when a warm engine is shut down, the temperature-sensitive clutch fluid will solidify, engaging the fan. When the engine is restarted--for example, the next morning when the engine is cold--the fan will run for a minuite or two until the clutch fluid re-liquifies.
 

·
Registered
Joined
·
2,097 Posts
The fluid in the clutch goes from one area of the clutch to the other as the temp tells it what degree of lockup it needs ,It does not "solidify" this will cause the fan to run at odd times , in the LLY overheating threads this has been refered to as "morning sickness" it is normal and common unless it runs excessivly when the air temp is cold , there is no rhyme or reason for it and it does not always happen if you want more info search "Overheating" and bring a comfortable chair and lots of beer as there is tons of material.
 

·
Registered
Joined
·
89 Posts
Discussion Starter #9
but can you guys hear your fan at idle? for example, yesterday I went about 40 miles and stopped for fuel. I could hear the fan on when I got out. Drove another 40 miles home, and jumped out and I could still hear it. It's 25 degrees here so it's not getting to warm. Fluid is good gauge is good?
 

·
Banned
Joined
·
1,390 Posts
I've noticed mine (LLY) runs at idle when the engine is warm as well, such as when I'm occasionally checking the trans fluid after I pull into the shop when I get home. Why, I don't know. I DO have the cold startup 'morning sickness' thing same as my '03 8.1 had. I believe they are unrelated. I also don't think the fan clutch continues to be engaged except at idle when warm, unless of course the temp calls for it to run. I also doubt if it's anything to worry about.
 

·
Registered
Joined
·
174 Posts
Fan also on once in a while at cold start, no rhyme or reason, but you will know when it is engaged as it sounds like jet engine at startup, have not heard it at all yet with heavy load.
 

·
Registered
Joined
·
89 Posts
Discussion Starter #12
It is on at idle all the time, warm or cold. You can open the hood and see it, hear it and defantly feel it! I took it to the dealer and they did a quick look. Tech said he was pretty sure it shouldn't do that! Goes in Monday morning!
 

·
Registered
Joined
·
682 Posts
Hello everyone,

I have had this same problem with several trucks (not Chevy's) that I have owned in the past. Also, while recently test driving Fords and Dodges prior to buying my Duramax, the same thing happened. Even several Toyota trucks I have owned have done this.

It seems like it's a fact of life with tuck motors.
 

·
Registered
Joined
·
174 Posts
It is on at idle all the time, warm or cold. You can open the hood and see it, hear it and defantly feel it! I took it to the dealer and they did a quick look. Tech said he was pretty sure it shouldn't do that! Goes in Monday morning!
Fan spins to some extent all the time, but when the clutch locks you will know, the nieghbors look every time i leave if the fan is engaged, but if you raise your hood it will look like the fan is running but is probably not fully engaged, this should be considered normal and not need to be repaired.
 

·
Banned
Joined
·
6,540 Posts
It is on at idle all the time, warm or cold. You can open the hood and see it, hear it and defantly feel it! I took it to the dealer and they did a quick look. Tech said he was pretty sure it shouldn't do that! Goes in Monday morning!
jbdmax, good post.

Roan, try a search. What you are seeing is the "thermo-viscous" fan clutch at it's evil best. "slip" drive mechanism, keeps the fan spinning 24/7. It must spin in order to work as designed. Also see the fins on the clutch. These are for dissipating the viscous heat created in full slip, and when engaged. The higher fan rpm during engagement is what creates the fan noise, mostly at the faster moving tips of the fan.

Your highway speed mileage should not be affected IMO. But the vehicle can drop over 20 HP if the fan engages. Of course that does reduce mpg, and as well the IAT goes up when this happens, dropping mpg further...
 

·
Registered
Joined
·
89 Posts
Discussion Starter #16
Just an update...

It was a bad sending unit! The fan was engaged but not all the way. I'm away from home, but dealer says it's all fixed!
 
1 - 16 of 16 Posts
Top