Cat 3406e fan staying on

With engine off apply air to fan and try to spin and listen for air leaking. When I had a mbn cat the connections on the two sensors would get loose and cause fan to kick in once in awhile ECM should be able to tell what's telling fan to turn on I think

 

You said in the post above "when I do that I hear air coming from clutch area," when you do what?

You shouldn't hear any air coming from fan clutch.

can you pinpoint where the air is coming from?

 

Fan hub probably needs replacement. Most likely you have a mysterious air leak due to hub leaking

 

Yup I would say fan hub or clutch, on mine there is an o-ring between the two, maybe that o ring is bad. You could have a crack in the hub I suppose. Either way you need to disassemble and determine where the leak is coming from.

 

Old post I know, I have the same engine my fan stays spinning at all times, but it’s not the high speed engine fan when temp gets too hot that spins much faster. Is that normal?

my question is for these 3406 5ek is the fan suppose to spin some at all times then engine fan engages once it hits a certain temp?

or is it suppose to not spin at all once air builds up and only come on when engine fan engages?

 

Your top plate is probably warped and grabbing the friction disc at some point causing it to drag.

If not that, the splined hub inside is likely dry or worn enough to not let the top plate fully disengage.

These are not two speed fans. Off and on only

 

I noticed that when my ac belt is off which it has been for a bit now the fan would come on and once air built it would shut off until temp reached where engine fan would engage

just put a new ac belt on and now the fan spins constantly slower than when the engine fan would once that’s kicked on if temp reaches level. Ac isn’t even working blowing cold might take the ac belt back off because the fan wasn’t spinning at all unless temp went up for it to engage. Just trying to figure it out really

 

With your engine off, can you spin the fan with your hand and have it spin freely for a bit?

 

yes if the air isn’t built up, when the truck sits over night I can pop the hood and it spins freely if the air is up after I shut the truck off it doesn’t spin.