Strange noise at idle

naturist · **Posted:** Mon Feb 17, 2014 5:32 pm

I'm thinking something isn't right, but so far the only symptom I've got is a strange noise at idle. I've got about 28,000 miles on a new timing belt and water pump installed at the same time we replaced the head and gasket 18 months ago. Still runs like a top, but I don't like this sound. The file is herehttp://www.expressions-photographics.com/forumpix/Engine_Noise.m4a, recorded beside the driver's side headlight. Anybody have any suggestions?

Yeti · **Posted:** Mon Feb 17, 2014 5:37 pm

it's a belt or some service pulley

dthdcrd · **Posted:** Mon Feb 17, 2014 5:48 pm

That's the sound my alternator decoupler made before I replaced it.

DOC4444 · **Posted:** Wed Feb 19, 2014 9:37 am

Could be any number of things, but most likely alternator decoupler. If you find telltale red dust around the alternator, that is it.

DOC

jsrmonster · **Posted:** Wed Feb 19, 2014 9:58 am

Yep - alternator pulley. http://www.idparts.com/catalog/product_ ... ts_id=2781
here is the tool tool tool http://www.idparts.com/catalog/product_ ... ts_id=3737

Jeff
http://rocketchip.com/coppermine/albums/uploads/alt_pulley.JPG

dieseldave · **Posted:** Wed Feb 19, 2014 5:47 pm

That is exactly what my CRD sounded like last week. I was 99% sure that it was the alternator decoupler but I was also worried that it was something worse because it basically sounded like someone threw a handful of nuts and bolts in the valve cover! I kept thinking that there was no way that the pulley could make that much clatter. I could not " feel " the noise but upon closer examination I saw the belt violently jumping off of the pulley as it went around. I spun the pulley after I took the belt off and noticed that the pulley had a wobble and that the pulley clutch was seized. I took the alternator to a local, "old school" starter & alternator guy and had him replace the decoupler and check out the overall condition. The replacement decoupler pulley was a " Made in Canda" Litens ...so I am confident that it will last for another 90K.

:shock:

I still can't believe how much clatter that pulley made! :shock:

Dave

camo · **Posted:** Wed Feb 19, 2014 11:10 pm

Decoupler or serpentine pulley...

camo · **Posted:** Wed Feb 19, 2014 11:30 pm

... and mocking bird.

MRausch82 · **Posted:** Thu Feb 27, 2014 1:30 pm

I was getting some strange "rotating" noise with my CRD for the past month. When it hit 100K this week, the noise got much worse. I diagnosed a bad alternator decoupler. I made a tool for my impact, and I just finished replacing it, and the thing is quieter than it has been in a long time. Still need to take it out for a long ride to see if it cured my issue, but I suspect it has.

arbby · **Joined:** Thu Oct 18, 2012 6:22 pm **Posts:** 27

Id defrost/ac on? Could be the compressor...

ebbnflow · **Posted:** Fri Feb 28, 2014 11:36 pm

Definately your alternator decoupler. Mine sounded exactly the same.

midlifejeepcrisis · **Joined:** Wed Jan 09, 2013 3:26 pm **Posts:** 18

My 2005 Liberty sounded exactly the same. Last fall I took it to a mechanic to do the timing belt/water pump change, and in the process found out it was a belt tensioner that was making the chirping noise. So it got replaced at the same time. Two months later I started hearing it again, usually most noticeable at startup when the engine was cold. Finally got around to checking into it today. The decoupler seems to be the culprit this time.

I bought my Liberty used from a stealership with around 84,000 miles on it. It now has 121,000. I'm assuming the decoupler/generator/alternator is the original. Anyone know the average lifespan of these things?

JGV · **Joined:** Thu May 15, 2014 11:59 am **Posts:** 1

I have the exact same noise at idle. Mechanic replaced the whole alternator. Also the belt , pulleys andtensioner was changed .Now he sais the crank pulley was on recall on the '06.
Is that true?

jthomas999 · **Joined:** Mon Jan 16, 2012 11:51 pm **Posts:** 98

I get about 90,000 or so per decoupler. I'm at 261,000 now on the 2nd replacement.

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factory53 · **Posted:** Wed May 21, 2014 2:37 pm

Is this tough to replace if you buy the tool from idparts?

Just wondering if I have to remove a bunch of components or parts just to be able to get at it.

Anyone done this before?

My Jeep makes the same chirping sound.

jthomas999 · **Joined:** Mon Jan 16, 2012 11:51 pm **Posts:** 98

I'm not sure if you have enough room to use the tool with the alternator on the vehicle, so you probably need to take it off. Once the alternator is off, the decoupler is trivial to replace.

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thermorex · **Posted:** Thu May 22, 2014 9:32 am

Even with enough room, I'd still take the alternator out, the pulley is pretty tied and use of a vice to hold the alt would be recommended. Also, not sure if it's right hand thread or left, but you can find out looking at how the belt moves.

factory53 · **Posted:** Fri May 23, 2014 3:54 pm

Thanks guys! I think I'll replace mine.

Just out of curiosity, when I put my AC on (which I'm happy to say we now have to!) the chirping gets really loud.

Would that still mean the decoupler?

thermorex · **Posted:** Fri May 23, 2014 4:03 pm

The ac puts extra load on the belt, so it makes sense to have the chirp louder. If you do t have a mechanical stethoscope, get a long screwdriver or a drive and touch with one end the alternator close to the pulley and on the other end close the hand like a fist while holding it, put your ear in the fist and listen to see if the noise gets louder. This way you can locate if the source of the noise is the decoupler.

factory53 · **Posted:** Fri May 23, 2014 4:40 pm

Thanks @thermorex! I'll give it a try!

Strange noise at idle

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