Serpentine belt/tenionser

MSJKU11

MSJKU11

Caught the Bug
Quick question. Belt popped off and replaced it and after about 5 minutes of driving the new belt popped off. Pulleys look good, everything moves freely. Thinking the tensioner is bad. Anything else to look for?

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My belt popped off. The actual bolt that holds the tensioner to the block was loose... as in 2 turns on the bolt to be finger tight. Check the entire assembly for play with the belt off.

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pedrosanchez1973 said:
Pull on the belt itself. Is there good spring tension? Maybe the idler?

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I pulled on the belt and had good tension. Runs idle just fine but when I drive it then it pops off after about 5 minutes

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do you till have the original belt? if so, compare the measurements.

not all aftermarket belts are the same length, I went thru this a while back and found as +/- 1/2" variance in the actual belt length.

I replaced the tensioner and idle pulley before I finally looked at the tension pulley and could see play in the belt as it was too long for the tensioner to take up proper slack. the slack was making a slapping sound on the backside of the tensioner.

Next belt I bought, different brand, same auto parts store, also specified for my jeep was too short and whined like a pig because it was too tight.

If you're still stock (no hydro assist etc...) get I'd get a Mopar belt.

Another thing to check is the pulley alignments. Make sure they are spinning true.

On my 2010, the idler pulley had a slope to the outer edge that allowed the belt to 'walk' off if any of the pulleys are out of alignment.
 
See if the belt comes off when ac is on or during a hard turn. You could have an AC compressor locking up or something going on with steering pump under load. If all is tight, you likely have a bad tensioner. I agree to check the belt length too.
 
Here is what I observed. The belt looks like it comes in at an angle to the tensioner from the crankshaft. When I crank it, the tensioner moves backwards then forwards and the belt pops off the crankshaft pulley.

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Here is a shot from the crankshaft to the tensioner 20180417_225705.jpg

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MSJKU11 said:
Here is what I observed. The belt looks like it comes in at an angle to the tensioner from the crankshaft. When I crank it, the tensioner moves backwards then forwards and the belt pops off the crankshaft pulley.
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that sounds like the belt may be a bit too long - that's the slop in the belt trying to be taken up by the tensioner or you've got the belt routed wrong.

hard to tell from that pic if the belt is coming up from under the crank to the tensioner - 3.8L belt route:

Belt_Routing.jpg
 
Being that it's shredded on the outboard side, make sure it's not rubbing on something, like a bolt, hose, sharp edge on pulley, etc. I realize that may have occurred when it came off as well, but seems strange that the entire circumference is fraying.
 
WJCO said:
Being that it's shredded on the outboard side, make sure it's not rubbing on something, like a bolt, hose, sharp edge on pulley, etc. I realize that may have occurred when it came off as well, but seems strange that the entire circumference is fraying.
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Yea it's the old belt and I can only think it was hitting something due to the misalignment. I have tried two new belts and the old belt and get the same results. I pulled the tensioner off and one of the bearings was busted and leaking grease. Not sure if that would cause the misalignment or anything else.

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MSJKU11 said:
Yea it's the old belt and I can only think it was hitting something due to the misalignment. I have tried two new belts and the old belt and get the same results. I pulled the tensioner off and one of the bearings was busted and leaking grease. Not sure if that would cause the misalignment or anything else.

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tensioner was bad? i was thinking it was good.
a bad tensioner would allow the belt to flop off.
may be what frayed the belt edge as well
 
jeeeep said:
tensioner was bad? i was thinking it was good.
a bad tensioner would allow the belt to flop off.
may be what frayed the belt edge as well
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I'm hoping that all it is. I'm changing it out tomorrow and we'll see.

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Welp got my tensioner replaced and new belt on and lo and behold. More squeaking and a loud clank. Found this big guy lying on the floor. Crankshaft pulley. I'm assuming I won't have the tools to replace this one. 20180421_225631.jpg

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MSJKU11 said:
Welp got my tensioner replaced and new belt on and lo and behold. More squeaking and a loud clank. Found this big guy lying on the floor. Crankshaft pulley. I'm assuming I won't have the tools to replace this one. View attachment 299780

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holy shit!

well, you could get the tools from your local auto parts store loaner tools.

motor still turns over ok? I've never seen one fall off like that, that's a shitty deal
 
jeeeep said:
holy shit!

well, you could get the tools from your local auto parts store loaner tools.

motor still turns over ok? I've never seen one fall off like that, that's a shitty deal
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Yep motor turns fine. I've never seen anything like this. Looks like I'll take a trip to the auto store tomorrow and see what I can do first. I can only imagine how hard it's going to be to get that bolt out. I only have a corded 1/2 impact

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