ATG: did I do anything wrong?

[alphatarget1]

My friend told me about his 1998 Jeep Grand Cherokee 4.0L being immobilized last night because of a broken drive belt. I offered to help him fix it. This morning we went to the parking lot with a drive belt bought from Autozone, I put it on without any issues. First start, one of the pulleys (next to the AC compressor) weren't moving and was rubbing against the belt. So I thought maybe the belt was too tight, or maybe they tightened the pulley too much. So I loosened the belt, loosened the pulley bolt next to the AC, and spun the AC idler pulley by hand. All seemed good, so I slightly tightened the pulley bolt, tightened the belt and tightened the adjusting pulley bolt, he started the car again and all was good.

This afternoon, he calls me and tells me the belt broke again. I went over to his house, found that the belt was shredded instead of snapped like last time (due to heat). I found that the AC pulley I loosened and retightened afterwards had become twisted to one side, and the mounting bracket is also damaged. The pulley was seized and shred to pieces. Now he needs a new belt, new pulley, AND a new bracket (or a used bracket from the junkyard).

I guess I should've known to say that the pulley was bad from the first start, instead of checking it by hand. The old belt snapped due to heat (can be seen from discoloration). Lesson learned? What would you have done?

 

[LTC8K6]

The serpentine belts have a tensioner, and should not need adjustment.

http://wjjeeps.com/serpentine.htm

 

[alphatarget1]

The serpentine belts have a tensioner, and should not need adjustment.

Nope, that is the newer model.

 

[LTC8K6]

I see what you did there...

 

[exdeath]

Did you pull the pulley and stick your finger though the inner race and try to spin it or did you just spin the pulley with a possibly already seized bearing over the loose bolt?

Also most OEM pulleys, especially stamped steel ones, are not reversible. Tightening them down one way will tighten them against the timing cover, bracket, etc and they won't be able to turn freely.

You can't tighten a pulley too much. If it's installed correctly, the tightness of the bolt has no effect on the pulley being able to spin (but you can still strip threads in the bracket, etc). All you are doing is securing the stationary inner race. If they pulley can't turn when locked down tight, it's either installed wrong (eg deeper side toward the inside and rubbing) or the bearing is seized.

 

[SabaII]

So you spun the A/C Idler pulley? What about the A/C Pulley? Rule of thumb when replacing a belt due to failure is to check all pulleys. Check that they spin free and have AT MOST very minimal play. Once you get the new belt on check the tension. Start the engine and make sure the belt is riding correctly in the pulleys. I always turn lights and A/C on just to make sure all is well. Do this every time you should never have a problem.

 

[alphatarget1]

Did you pull the pulley and stick your finger though the inner race and try to spin it or did you just spin the pulley with a possibly already seized bearing over the loose bolt?

Also most OEM pulleys, especially stamped steel ones, are not reversible. Tightening them down one way will tighten them against the timing cover, bracket, etc and they won't be able to turn freely.

You can't tighten a pulley too much. If it's installed correctly, the tightness of the bolt has no effect on the pulley being able to spin (but you can still strip threads in the bracket, etc). All you are doing is securing the stationary inner race. If they pulley can't turn when locked down tight, it's either installed wrong (eg deeper side toward the inside and rubbing) or the bearing is seized.

I don't think the bolt was loose enough that the pulley was simply spinning on the loose bolt. The weird thing is, the pulley was secured by a bolt and a big fat washer that covered all of the bearing, instead of just the inner race. I think I should have checked it more carefully. It's just that it was in a bank's parking lot and I didn't want to pull the pulley out and test it if I can get it to work without pulling it out, I didn't expect it to cause damage. Oh well.

 

[alphatarget1]

So you spun the A/C Idler pulley? What about the A/C Pulley? Rule of thumb when replacing a belt due to failure is to check all pulleys. Check that they spin free and have AT MOST very minimal play. Once you get the new belt on check the tension. Start the engine and make sure the belt is riding correctly in the pulleys. I always turn lights and A/C on just to make sure all is well. Do this every time you should never have a problem.

Everything was working fine afterwards. AC kicked on fine, really nothing was wrong with it. I suspect the bearing on the pulley was on its way out...

 

[Ferzerp]

I had a car with a seized AC compressor once. Once the clutch engaged to turn on the compressor, the pulley would stop turning, building up heat and would eventually shred the belt, or, if it lasted until you stopped, melt the belt after a stop. That was fun.