Fan stuck (Cummins isx)

Is the fan hub getting air pressure? Depending on the model of the truck the solenoid for the fan may be located on the firewall. Unplug the air line coming out of it to the fan. Start the truck up and let the air pressure build up. At around 90 psi there should be air pressure coming out of the solenoid. If it does then the fan clutch is the issue. If not the solenoid is the issue. Clutches when they sit for a long time do have a tendency to stick just like brakes on some trucks.

 

I don't know about the Cummings on one of the cats I had you could hook air from an air hose direct to the fan hub turn the air on and off to see if the fan released was how he checked to see if it was the fan or solenoid .But I'm not a mechanic just watched the guy doing it

 

Usually the air pressure allows the fan to spin freely, no air pressure and the fan clutch is engaged.

 

Mine sticks on occasion. Typically when I first start out. Sometimes won't happen for weeks. When it does, it will stick for 10 to 15 minutes.
I also think this is some sort of corrosion issue in the fan clutch. My wrench tells me it probably is the fan clutch. He said it has like a fail safe to it, so that when it goes out it locks in, and will run constantly, so that it doesn't leave you walking.

Please post what you find, if you find it before I do.

 

The fail mode on the fan clutches are when there is no air to the they stay in the on position.

 

My only experience with this (same engine by the way), is the fan will NOT free up. I ran about 2,500 miles and it never freed. Got about 4.8 mpg too during that time (according to the onboard computer)---truck was a rental, so I told them about it when I turned it in---then walked away, so I don't know what the 'fix' was.

 

My t800 fans comes on when I crank her, no air fan is engaged. Until it reaches about 80 on mine.
So do like the guys said, pull air line after you build pressure and see if it is getting supply, if not it is engaged. After this step start trouble shooting relay, or temp sensor.