Went to replace the tensioner and idler pulleys on a 96 4.3 2wd with 182K. I'm sure they were the originals. Not making any real racket, just some chirp at start-up, but since it's an easy R and R, just thought I'd add this to some other recent maintenance.

The new idler pulley would not turn by hand when the bolt was tightened, so I tightened just enough to allow the pulley to turn by hand. Pulley chirped during test drive.

So I tightened it to what felt like an appropriate torque, though still wasn't comfortable with the fact the pulley wouldn't turn by hand at this torque. The original pulley turned freely by hand. I figured that must have been due simply to wear. I installed the new one (standard Duralast from AutoZ) exactly as the old one had been installed (retaining split washer and spacer).

The chirping ended, but I'm standing there watching it...and the pulley flies off, bounces into and off of the fan and onto the ground! Cut the engine, and found the bearing still bolted on. It was very hot. I think I heard it sizzle. Maybe just my fingers when I went to remove it.

Has anyone experienced anything like this? Swartlkk says the pulley should spin freely, and another member says the torque for that bolt is 37 ft. lbs. I'm sure I was shy of that torque, and the pulley would not spin by hand.

Can anyone confirm the correct torque for this bolt, or offer any ideas why this pulley would not turn by hand when the bolt was tightened? It's as if I installed it incorrectly, but in retracing, I can't see where. Does anyone know of a diagram of how this simple pulley is attached, just to confirm?

Thanks in advance for any insights!

 

The bolt should tighten down on the inner race of the bearing, not the outer race, leaving the pulley to spin free. It sounds like the pulley you were given did not allow this to happen...

Without looking it up, 37 ft-lbs sounds appropriate for the tensioner bolt.

 

Thanks, sounds perfectly reasonable, will see if I can make sense of it in those terms soon as I can peel away from this desk...

 

+1 - what swartlkk said.

Make sure you didn't install the spacer backwards/flipped around. On my '97, I found that installing it one way (the right way) had the spacer make contact with the inner race, and flipping it around the wrong way had it make contact with the outer race. When on the inner race, you can crank right down and the pulley spins freely. You get resistance when the spacer is on the outer race, which would explain why it would get harder to turn as you tightened the bolt.

 

Looks like my issue was the large washer at the front (toward the front end of the truck) of the bearing, just underneath the bolt itself: I think I installed that backward, so it's outer ring was pressing against the outer race of the bearing (can't be 100% sure because I've already reinstalled the old one for comparison). I'd insert this Smilie here where the doofus is smacking his forehead, but that doesn't come anywhere near a capture of my sentiment right now. Perhaps if he had a hammer in his hand...

Thanks to you both for pointers to what should have been the obvious.

I'll now busy myself concocting a story for AutoZone about the gremlins that made the mysterious idler pulley fly off its bearing. Wish me luck.