Fan Pulley Studs Thread Engagement - 1997 4.0

[Stinkbug]

I am at the end of putting my Jeep back together after refreshing my cooling system. I noticed something that is going to bother me so I will risk the dumb question to allow me to sleep well at night rather than dwelling on this stuff...

I swapped the fan pully studs from the old water pump to new pump. I didn't pay attention when I took it apart so maybe it's nothing... But i noticed that the studs on the water pump are not very long and don't allow the nuts to be fully engaged. The stud is about a thread short of the top of the 5/16-18 nut that has the free spinning external tooth lock washer connected to it.

In the back of my mind there is something that is nagging me saying you need one to two threads sticking out of the nut to have full clamping force. I have a vision of the nuts coming loose and the fan spinning off and taking out my new radiator.

Thoughts?

 

[KennethS]

Mine have always transferred without any issues. How far are the studs into the water pump flange?

 

[Stinkbug]

I tightened them down until they hit the un-threaded portion of the stud and they seated. Maybe that was not necessary?

 

[KennethS]

Were they that way when you removed them? If the water pump flange and fan clutch flange are the same thickness as the originals, the studs should work the same as before.

 

[Stinkbug]

Didn’t swap the fan clutch… as I think this through I think I am going to:

1. Take the fan assembly off
2. Pull the fan pulley off
3. Check how much of the stud is exposed on the back side of the water pump and if there is excess back them out a bit.
4. Put it all back together with the studs protruding a bit further forward.
5. Assume that even if the studs are not fully seated, the clamping force will hold it all together.

Or more likely just find some flange bolts that will fit.

 

[Stinkbug]

In my typical fashion I think I over thought this one and created a problem where none exists. The solution seems simple.

Maybe the studs do not need to be jammed all the way down to the non threaded portion. Maybe they only need to be threaded down far enough to slightly protrude from the water pump flange. That will leave plenty of thread on the other end to secure the fan. Maybe the nuts holding the fan clutch will provide all the clamping force necessary since the essentially turn the studs into a bolt.

 

[machoheadgames]

In my experience the studs needed to be bottomed out in the water pump so they didn’t unthread when I removed the nuts from the fan for future work….

 

[KennethS]

In my experience the studs needed to be bottomed out in the water pump so they didn’t unthread when I removed the nuts from the fan for future work….

I’ve had that happen a time or two. Not an issue as the stud and nut came out the same as if it were a bolt. Reassembling was a pain, though, and I discovered why studs are used instead of bolts. Finally took the nuts off and installed the studs to guide the fan flange, then put the nuts on last.