Failed serpentine belt roller idler

OffRoadTrain · **Joined:** Thu May 21, 2015 10:09 pm **Posts:** 11

My CRD was sounding extra rough, and occasionally it would make some grinding sounds. It was hard to pinpoint but seemed louder on the driver side. It would frequently be heard at start up then lessen/disappear shortly after. After these videos I parked it (wish I had the camera running right at start-up, neither really capture the sound very well); now that the weather is decent I took another look, unlike in the video it’s now obvious that serpentine belt roller idler is no good.

bad serpentine belt roller idler video part 1
https://youtu.be/5TTg86xhtmE

bad serpentine belt roller idler video part 2
https://youtu.be/4GC1yTTLLx0

Picture of it failed
https://www.dropbox.com/s/9p6xapkjir0xl ... r.JPG?dl=0

Is this an isolated issue or do you figure there is an alternative underlying issue such as a bad alternator decoupler or bad harmonic balancer? The serpentine belt tensioner was replaced 2 summers ago, total mileage 125K or ~200KM. The belt was fine and was not replaced.

Should I also go in and replace other parts? According to this thread I need 3 rollers - one for the serpentine belt tensioner... This doesn't seem right since ID Parts states two:
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=69705

Mike92104 · **Posted:** Sat Apr 30, 2016 7:03 pm

From your picture, it looks like there is some corrosion on the pulley bolt. Is it possible that pulley was getting wet somehow?

3 idler pulleys is correct. 1 of them is used to replace the tensioner pulley.

OffRoadTrain · **Joined:** Thu May 21, 2015 10:09 pm **Posts:** 11

Took the belt off and there is corrosion but not on the bolt just the roller and internal to the roller. Fell right apart and the bearing portion was sheared.

The other roller makes a bit of noise and has some rust spots on it but spins ok. The roller on the tensioner hardly spins.

The top left & bottom right pulleys spin freely, the alternator spins in both directions just fine. I'll replace all three rollers.

WWDiesel · **Posted:** Sun May 01, 2016 10:49 am

If your serpentine belt is bouncing bad at idle, one of these items can cause the problem....
Pop the cap on the alternator pulley and look for any signs of red dust (rust), if you see any, replace alternator pulley. You can also test the alternator pulley while you got the cap off by holding the alternator shaft with a wrench and turning the pulley by hand. You should be able to turn the pulley by hand in only one direction with some resistance. (override clutch). If you cannot, it is locked up and should be replaced! If it does not function, it will put added strain on the other belt pulleys...
The tensioner spring gets weak with age and does not keep proper tension on the serpentine belt allowing it to bounce which puts added strain on the other pulleys. While you are in replacing pulleys, you may want to go ahead and replace the tensioner pulley assembly as well... :wink:

funnyman06 · **Joined:** Sun Jul 06, 2014 7:46 pm **Posts:** 180

Having fought with all of these pieces I would replace the idlers, the tensioner, the belt, and the decoupler with the updated one. Also if you having issues with your crank pulley I had to replace mine because the bolts got loose and started working opening up the holes. After replacing everything I now know that it should be good for a while.

OffRoadTrain · **Joined:** Thu May 21, 2015 10:09 pm **Posts:** 11

Popped the cap of the alternator decoupler and there was lots of black/red powder and chips. I'll test it when I go to replace it, ordered the decoupler and 3 idler rollers. Took out the belt and started up the jeep and she sounds healthy again.

funnyman06 · **Joined:** Sun Jul 06, 2014 7:46 pm **Posts:** 180

good plan

WWDiesel · **Posted:** Tue May 03, 2016 9:46 am

OffRoadTrain wrote:

Popped the cap of the alternator decoupler and there was lots of black/red powder and chips. I'll test it when I go to replace it, ordered the decoupler and 3 idler rollers. Took out the belt and started up the jeep and she sounds healthy again.

Be sure and check the tensioner spring tension as the spring gets weak with age and does not keep proper pressure on the serpentine belt . You may want to replace it while you got everything apart. I was amazed at the difference in tension between the old one and the new one when I replaced mine a couple years back.... :wink:

OffRoadTrain · **Joined:** Thu May 21, 2015 10:09 pm **Posts:** 11

Replaced belt tensioner not too long ago, believe to summers ago so I did not order it.

Two the or rollers I removed weren't in great shape one definitely failed, however, the third roller doesn't fit on the lower left hand roller. The new bolts are longer and larger (16mm vs 15mm) plus the original doesn't come with a washer. Picture's attached

Location of removed roller (bright white spot)
https://www.dropbox.com/s/rbju467fjtt218a/DSC_0415.JPG?dl=0

Old roller on the left, new idler roller on the right
https://www.dropbox.com/s/9dq0keyy0d7mg7m/DSC_0418.JPG?dl=0

Do I remove that washer somehow and replace with the smaller bolt?

Rixram · **Posted:** Sun May 15, 2016 8:20 pm

I've had this happen before.

The Alternator decoupler is going bad, and causes bouncing in the system. The system really doesn't like bouncing. It caused my serp belt tensioner to fail. It also caused damage to a pulley/roller idler, which failed 2 months later.

You're replaced the decoupler, it appears. I'd recommend replacing the serp belt tensioner and the 2 pulleys/Roller Idlers as well.

Failed serpentine belt roller idler

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