Horton clutch fan

Another thing to check, after having the engine run for a few hours. Check with your hand and see if any of the tension pulleys are hot to the touch, even the fan hub. If any of them are to hot to touch or hotter than the rest. I would start there.

 

You have the HTS model most likely, they last a long time, good hub.
When the early emission engines started to come out in 2004-5 they required a fan hub engaged if air was lost, a fail safe "on" design.
Paccar went with the Horton Drivemaster hub that had a lot of failures so later went with Borg Warner, which had an even worse failure rate, so they are back to Horton that is a "two speed" as it has magnets in it so its always spinning, makes engagement easier on the friction disc, but tends to over cool in winter low temps, causing other issues (egr etc).

 

I agree. Those Horton hts are bullet proof.

 

Mine is specific to the CAT 3408, won't fit anything else. The bearings are huge, but smaller bearings come into play when the fan is engaged, the big bearings just freewheel. That's why it's not a good idea for the fan to be engaged for too long. If anything fails you can lock it in with bolts that Horton supply. So it isn't fail safe like the later ones that's for sure.