Lots of noise under the hood from my serpentine belt

Greenwing7 · **Posted:** Tue Jun 02, 2015 4:47 pm

as the post reads, lots of noise from my serpentine belt. It really picks up when I turn the A/C on, almost a grinding like noise with some squeaks in the belt at idle RPM. How can I determine what parts to look at are causing the problem? I would like to specifically rule out alternator clutch (alternator replaced <6 months ago, tensioner, and A/C clutch/motor. The A/C still blows very cold air.
thanks Ill start looking when I get some ideas.
TW

thermorex · **Posted:** Tue Jun 02, 2015 5:17 pm

Maybe a pulley? Get a mechanical sthetoscope and start listening to everything that moves with the belt.

papaindigo · **Posted:** Wed Jun 03, 2015 7:40 am

At idle look down the serp belt, may have to remove plastic engine cover, is the serp belt tensioner bouncing or barely twitching - repeat with AC on. If bouncing it's the alternator decoupler pulley. If not it's one of the others. But I suspect alternator not withstanding replacement as decouplers can fail early or perhaps your replacement did not have the proper decoupler pulley.

Greenwing7 · **Posted:** Sat Jun 06, 2015 12:59 pm

what would it be doing if the accesory tensioner (spring) was going bad?

WWDiesel · **Posted:** Sat Jun 06, 2015 1:13 pm

Could be a weak spring in the tensioner pulley or a bad alternator decoupler pulley as Pap stated. Either one or a combination of both can cause the belt to bounce fairly bad at idle especially with the AC comp. on.... :wink:

papaindigo · **Posted:** Sat Jun 06, 2015 1:33 pm

To the extent I recall serp belt spring problem posts either the tensioner housing has cracked or when the belt is removed the tensioner "leans" into the power steering pulley instead of staying straight. How it behaves at idle if the spring is bad I have no clue.

WWDiesel · **Posted:** Sat Jun 06, 2015 3:25 pm

The spring in the tension does get weak over time; there was a very noticable difference between the old one and the new one when I replaced my tensioner some time back. The new one stopped the bouncing problem at idle along with a new decoupler alternator pulley... :wink:

weeks101 · **Joined:** Mon Jul 30, 2012 3:29 pm **Posts:** 747

Did you replace the belt with a new one when you replaced the alternator?

Greenwing7 · **Posted:** Sun Jun 07, 2015 11:46 am

weeks, No, the belt was <1 year and 5k miles old, this is my 4th alternator in <18mo and its been the decoupler every time, im putting another free replacement on and going to an alternator shop (if in fact thats my problem here again) and getting the upgraded decoupler.
Im replacing/trouble shooting tomorrow on my day off and will keep yall posted

Greenwing7 · **Posted:** Tue Jun 09, 2015 5:50 pm

thank you to everyone who responded, indeed there was a large wobble in the belt just below the alternator when the A/c was turned on. The alternator decoupler was AGAIN SHOT! This is my 4th alternator in 15kmiles. what are the aftermarket options for decouplers that won't break the bank?
if these are infact a high quality unit that may out last the alternator, can they be installed on a new one? BTW my alternaors have been from O'rileys and are stamped made in mexico.

flash7210 · **Posted:** Tue Jun 09, 2015 6:01 pm

Litens 920834
should be available from advance auto parts.

I found a local starter/alternator shop that had one in stock, pulley+installation for $50.

WWDiesel · **Posted:** Tue Jun 09, 2015 9:28 pm

AS flash stated, find yourself a local alternator / starter shop and buy a decoupler pulley from them, they should have a high quality pulley for less than 50 bucks....and probably will install it for free if you bring them your alternator.... :wink:

kencary · **Posted:** Wed Jun 10, 2015 11:23 pm

I nave a slight squeak upon starting that that goes away after a few minutes of running or if the AC is turned off.

I replaced the belt and tensioner a few months ago, but I am wondering if the alternator decoupler is going.

That would make sense as the most load is on the alternator pulley after starting the engine as the battery is recharging to replace the juice used in starting.

The tensioner does bounce a bit.

What is the best way to tell if the alternator is going?

papaindigo · **Posted:** Thu Jun 11, 2015 8:25 am

Tensioner should just barely twitch. Alternators don't often go but any decent parts store can test it's output. The alternator decoupler does, however, go which causes a squeak and decoupler bounce. Pop the plastic cover off the front of the decoupler and look for lots of red dust; if present replace decoupler as noted above.

kencary · **Posted:** Thu Jun 11, 2015 9:14 am

Thanks for the advise.

While I have the Liberty to work on the Turbo hose, I will check it out.

Why is there even a decoupler on this alternator? Why don't they just have a simple pulley?

Tree Catcher · **Posted:** Thu Jun 11, 2015 6:39 pm

I did not have the dreaded red dust but I did have plenty of dark brown or black dust along with the noise with the A/C on. 65 dollars later and I have a new pulley on the alternator. Now all I have to do is put the alternator back on the jeep. From what I was told, the old pulley was just about to self destruct, it came apart in pieces. So if anyone in the Southern Ca. area namely Riverside needs one this is where to go Inland Alternator Starter on Indiana St.

Sean

weeks101 · **Joined:** Mon Jul 30, 2012 3:29 pm **Posts:** 747

kencary wrote:

Why is there even a decoupler on this alternator? Why don't they just have a simple pulley?

http://www.litens.com/vibprod1.cfm

https://www.youtube.com/user/LitensOAD/videos

JHolm · **Joined:** Mon Nov 10, 2014 11:05 am **Posts:** 45

I bought a crd where someone had changed the alternator with one that didn't have the decoupler pully. It took me a while to figure out (with the help of this forum) that I need one to cure the anoying noise it made at idle. I bought one and it fit right in place of the if fixed pully. Thanks weeks 101 for the link, I was wondering what the purpose if it was.

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Lots of noise under the hood from my serpentine belt

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