I am wondering what the clutch fan is for? Sometimes when out on the interstate crusing along and go for an exit, it sounds like their is another fan running for a little bit but the engine temp never changes. I notice this in the summer times here in Ohio. Also when it is cold and for the first minute or two in the mornings until she gets warmed up, it sounds like thier is something else running too.....THANKS!!

 

I've noticed that too. Sounds like the fan is spinning much faster all of a sudden. I usually notice it in warmer weather, about 80° and up. I hope someone can shed some light.

 

well it doesn't sound like a problem to me. I have owned 3 PSD's and they all did it. I just assumed it was part of the cooling system. We have detroit series 60 in our fire trucks and they do the exact same thing. maybe somebody will shed some light for you.

 

COme to think of it, our 7.3 PSD ambulances do that also.....humm....

 

it is my understanding that a clutch fan is a "variable speed" setup that is temperature controled... the fan kind of "free wheels" around the shaft under normal operating conditions, it does move some air, but not as much as it can, because the cooling system is so large you don't need to run the fan at full bore most of the time... by free wheeling, mostly, you save fuel and noise.. now, when you are running on a hot day, running the ac, or towing, as long as you are at highway speeds, your fan clutch will just keep free wheeling, but slow down, or pull a really big hill at slower speeds, and your cooling system will fully engage the fan clutch and man she'll blow some air..! this is a two stage design on the cooling system, needed because diesels can do so much more work than a gasser, but they don't need it all the time... btw... if you've ever go walkin' by a peterbuilt or other highway tractor that just came off the highway on a hot day and it's sitting there idling and then the fan kicks in.... watch out..! you may have to go change your shorts..!

somebody clue me in if i'm wrong, or i left something out...

i know what i forgot... winter... when you run the defrost, in most vehicles you are also running the ac, the fan clutch is sometimes activated if you turn on the vehicle with the ac on.. the idea is to make sure the ac condensor doesn't get too hot, and until the system figures out that it is cool it runs the fan clutch as a "fail safe" just to make sure... if you start your truck in the summer and you left your ac on, you will probably notice the same thing...

 

no, i think you hit it right on the head. the fire engines do the exact same thing. i never gave it a second thought with my psd. i think medic 66 has nothing to worry about. i would chalk it up to one more awesome sound the psd makes as it roars to life!!!

 

Sounds great to me too....love every noise the ole' girl makes!!!

 

i second that... i love the sounds my mule makes... i love the way she "barks" when she starts... i love the fan when she's cranking, although i rarely hear that... and i love the "jet plane" sound she makes when she's warming up in the winter...!