AC / pulleys/ serp-belt noise?

dgeist · **Posted:** Mon Aug 25, 2008 3:53 pm

So, I've been having a progressively louder noise coming from the front of the jeep, most noticeable at idle, but easily audible from outside while at speed. Here are the symptoms:
- low grumbling sound, like a dampened metallic rattle that corresponds to engine speed (pitch, the same, just vibration/grumbling gets faster)
- chirp/squeak noise coming from the same area as the grumble, and alternating (i.e. if it's chirping, the grumble will stop for a bit and vice versa)
- sounds MUCH worse when the AC compressor kicks on. I can use the AC dash button to almost turn the noise on/off

I'm thinking I have a serp belt/pulley issue but don't want to spend 3 hours taking it to some bozo at a dealer who may or may not diagnose it right. I'd like to at least diagnose it myself. I have about 31k miles, so it's a little early, but I use AC almost all the time, so this may not be that odd for the mileage. I'd like to know how to verify what's making the noise. I've heard of the screwdriver test, but how can I put that on the idlers and tensioner? Does the spring tensioner itself usually need replacing, or is it usually just the pulley that dies? If I pop the belt off to inspect, is a worn pulley obviously so when you spin it by hand?

Thanks.
Dan

gmctd · **Posted:** Mon Aug 25, 2008 4:00 pm

It's the torque-reactive alternator pulley and the super-compliant serp belt - depending on the mileage, could also be the idler pulleys are running dry - this isn't the first time this has been brought up, nor will it be the last: only way to identify with the noise is to experience it - new alt pulley will heal it for approx the same mileage interval - I take mine outta gear at stoplites: saves the trans fluid, saves fuel, don't make as much noise, eh.........

FYI: that noise is indicative of the low rpm reactive forces the serp belt is being subjected to in this 2.8L 4cyl Diesel engine - they're the same at higher rpm, but seem smoother due to inertia

dgeist · **Posted:** Mon Aug 25, 2008 4:10 pm

K...Why the alternator if turning the AC on/off seems to change the noise? Also, can I tell if the idlers are bad sans-belt if I'm touching them? Can you explain the screwdriver trick (what to listen for) so I can diagnose this myself and save some time?

Dan

{update}
just found http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?t=32742&postdays=0&postorder=asc&highlight=pulley+belt+alternator&start=0 and
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?t=29055&start=0

So, I'll try to glean some knowledge there. It would be nice to know if anyone can explain the ear-to-screwdriver method, though

gmctd · **Posted:** Mon Aug 25, 2008 4:47 pm

Place the tip of a long scredriver on the suspect item - place the ear on the handle end of the handle - if that's not the noise, move the tip amongst various suspicious item till you find the noise you hear - reactive inertia changes from ac comp load and increased alt draw, increasing crankshaft loading - noise changes - put it in gear with the ac on, the noise reboubles in volume, usually - the lower the rpm, the greater the reactive forces, the louder the noise

dgeist · **Posted:** Mon Aug 25, 2008 10:09 pm

gmctd wrote:

Place the tip of a long scredriver on the suspect item - place the ear on the handle end of the handle - if that's not the noise, move the tip amongst various suspicious item till you find the noise you hear - reactive inertia changes from ac comp load and increased alt draw, increasing crankshaft loading - noise changes - put it in gear with the ac on, the noise reboubles in volume, usually - the lower the rpm, the greater the reactive forces, the louder the noise

So, I did the screwdriver test against a couple components on the belt path. The only difference is that on the Alternator, there's a deep "whir-whir-whir-whir" where the other components had a constant gentle hum. I stopped by a dealer and they said it couldn't be just the pulley since it doesn't have any bearings in it, which sounded logical. Why exactly is it just the pulley that causes the problem?

Dan

gmctd · **Posted:** Mon Aug 25, 2008 10:28 pm

It's a rubber-mounted one-way-clutch, absorbs the accel\decel forces of the comparitively large 2.8L 4cyl Diesel crankshaft - the serp belt is also made very compliant to help absorb the shocks - you may notice it is very soft compared to a gates or goodyear or napa or autozone aftermarket belt

dgeist · **Posted:** Tue Aug 26, 2008 9:38 am

gmctd wrote:

It's a rubber-mounted one-way-clutch, absorbs the accel\decel forces of the comparitively large 2.8L 4cyl Diesel crankshaft - the serp belt is also made very compliant to help absorb the shocks - you may notice it is very soft compared to a gates or goodyear or napa or autozone aftermarket belt

So, is the cyclic grinding noise, in fact, a bearing or something else in that clutch that's dying? I'm just trying to get my ducks in a row so when I ask the dealer to pre-order some parts, I have a good explanation.

Dan

gmctd · **Posted:** Tue Aug 26, 2008 10:55 am

Just axe fo' th' 2.8L CRD alternator pulley - they'll know what you mean - 53013554AE

Might get the two idlers, while yer at it - 5066938AA

ATXKJ · **Posted:** Tue Aug 26, 2008 1:30 pm

If you know what you want and that they'll probably have to order it - short circuit the process and order your own
http://www.moparpartsamerica.com/partlocator/index.cfm?action=searchCatalogOEM&siteid=214583

MACKJ · **Posted:** Thu Aug 28, 2008 9:47 am

dgeist wrote:

gmctd wrote:

It's a rubber-mounted one-way-clutch, absorbs the accel\decel forces of the comparitively large 2.8L 4cyl Diesel crankshaft - the serp belt is also made very compliant to help absorb the shocks - you may notice it is very soft compared to a gates or goodyear or napa or autozone aftermarket belt

So, is the cyclic grinding noise, in fact, a bearing or something else in that clutch that's dying? I'm just trying to get my ducks in a row so when I ask the dealer to pre-order some parts, I have a good explanation.

Dan

Dan,
Sounds like the bearing going in the alternator pulley, yes they do have one that allows the alternator to spin down upon the violent diesel shutdown.
You could also try an aftermarket Dayco brand serpentine belt, part number 6PK2870 (1130K6). I have been running one for some time now with no issues, very quiet.
When you order the pulley don't forget (like I did) to ask for the little plastic cover on the front.

kccrd · **Joined:** Thu Mar 08, 2007 10:35 pm **Posts:** 267

There are three idler pulleys, one in the middle one below the alternator and one on the belt tensioner all are the same at least that I could tell I took them all off the other day and cleaned them. They all seemed to have a urethane bushing that the collar and the bolt goes through there is also a flat collar that unscrews on the back side of all three. Mine had quite a bit of caked on dirt riding within the pulley itself but a couple of times around with a small screw driver and some compressed air and it came clean. I am at 85,000 now and they seem to run quieter now with that little cleaning. I also had to replace the pulley on my alternator with a regular pulley which is working just fine but have the original on order from the dealer they will give me the internet price of $53.00. I am going to put on a new belt when I replace that pulley. Good luck

KeighJeigh · **Posted:** Thu Aug 28, 2008 1:26 pm

gmctd wrote:

Just axe fo' th' 2.8L CRD alternator pulley - they'll know what you mean - 53013554AE

Might get the two idlers, while yer at it - 5066938AA

What timing!

I logged on to the forum with the intention of asking about these part numbers because the 2 dealers I called told me this part was not available seperately and I was required to buy the whole $*#$ alternator for $400.

Looks like $54 from Moparpartsamerica instead.

I'm not sure about adding another $150 for the other pulleys though......my car has less than 40k on it. But then again.. :roll:

Thanks!

Chris

kccrd · **Joined:** Thu Mar 08, 2007 10:35 pm **Posts:** 267

The other pulleys are not needed unless the bushing in the center is wearing out and allowing the pulley to move up and down. It looks like the pulley on the belt tensioner might only come with the tension but I think differently, they all looked the same. I should have made note of the part#s on the back of the pulleys maybe when I put the new alternator pulley on I will take the tensioner pulley and one of the other idler pulleys and compare part #s they sure look the same to me. So far I have been using a normal type pulley that a alternator shop owner gave me and it has been performing great. I have put about 700 miles with it on the vehicle so far and no problems.

dgeist · **Posted:** Fri Aug 29, 2008 1:11 am

so, since I'm still in the warranty period, I'll be darned if I'm going to special order parts and troubleshoot this all myself IF I can find a shop that'll work with me. Well, I did that. Although one dealer is 1.5 miles from my house, I went to the one 10 miles away because they were willing to listen to what I'd already done (and the service writer agreed with all the steps taken thus-far) and were also willing to schedule a 1-hour block in the AM the other day just to have it in to diagnose which parts are dying.. .and give me a quick car wash

Long story short, they put in an order for two parts:
56044672-AB (Alternator)
5066938-AA (idler pulley)

Now, I assume that they either figure my chattering tensioner pulley should just be replaced since it's absorbing a lot of abuse or they found something I hadn't noticed. As for the Alternator, I'm fine with them replacing it as long as the pulley gets replaced too... Anyone know if a new alternator comes with a pulley or if this shop is missing one item from the checklist.

BTW, both them and moparpartsamerica had to special order if from the warehouse in Milwaukee

Dan

KeighJeigh · **Posted:** Sat Aug 30, 2008 8:21 pm

dgeist wrote:

so, since I'm still in the warranty period, I'll be darned if I'm going to special order parts and troubleshoot this all myself IF I can find a shop that'll work with me. Well, I did that. Although one dealer is 1.5 miles from my house, I went to the one 10 miles away because they were willing to listen to what I'd already done (and the service writer agreed with all the steps taken thus-far) and were also willing to schedule a 1-hour block in the AM the other day just to have it in to diagnose which parts are dying.. .and give me a quick car wash

Long story short, they put in an order for two parts:
56044672-AB (Alternator)
5066938-AA (idler pulley)
Now, I assume that they either figure my chattering tensioner pulley should just be replaced since it's absorbing a lot of abuse or they found something I hadn't noticed. As for the Alternator, I'm fine with them replacing it as long as the pulley gets replaced too... Anyone know if a new alternator comes with a pulley or if this shop is missing one item from the checklist.
BTW, both them and moparpartsamerica had to special order if from the warehouse in Milwaukee

Dan

You are lucky. Thus far, the stealers I have dealt with all go completely by the book: If it's past 36 months then it is only covered if it is part of the drive train. End of conversation. I consider the warranty more or less meaningless.

dgeist · **Posted:** Sun Aug 31, 2008 8:08 am

KeighJeigh wrote:

You are lucky. Thus far, the stealers I have dealt with all go completely by the book: If it's past 36 months then it is only covered if it is part of the drive train. End of conversation. I consider the warranty more or less meaningless.

I have 31k and have only owned it for 29 months. I'm getting everything checked out NOW...

mrkake · **Posted:** Sun Aug 31, 2008 5:13 pm

The Alternator does come with the pulley pre-assembled. Is there a part number for the little plastic cover? Can I reuse the old one? Just to make sure I am diagnosing this correctly as well . . .

When the AC compressor kicks on I get a squealing chatter. If I turn off the AC or slip it into neutral it goes away. It seems to go away when I am driving at nearly any speed (hard to tell though). I thought my AC compressor clutch was going out, but you guys are saying that since its a torque-reactive alternator pulley, when put under load it squeals. Right?

I changed my belt and cleaned the pulleys which helped but didn't fix the problem.

KeighJeigh · **Posted:** Sun Aug 31, 2008 6:14 pm

mrkake wrote:

The Alternator does come with the pulley pre-assembled. Is there a part number for the little plastic cover? Can I reuse the old one? Just to make sure I am diagnosing this correctly as well . . .

When the AC compressor kicks on I get a squealing chatter. If I turn off the AC or slip it into neutral it goes away. It seems to go away when I am driving at nearly any speed (hard to tell though). I thought my AC compressor clutch was going out, but you guys are saying that since its a torque-reactive alternator pulley, when put under load it squeals. Right?

I changed my belt and cleaned the pulleys which helped but didn't fix the problem.

This is my exact situation.
I'm only going by what I see & hear as well as the advice from this forum.....but it does make sense so I'm going to go ahead and change the pulley.

kccrd · **Joined:** Thu Mar 08, 2007 10:35 pm **Posts:** 267

I put a little dielectric grease on the belt in 4 to 5 spots across the ribs of the belt smeared it around a little and all chirping went completely away. A service manager a my local jeep dealer told me to do it. Worked great but I just changed the alternator pulley and cleaned all the other idler pulleys and put some high temp grease in the middle shaft to make sure they ran smooth. Give the grease a try does not cost much.

mrkake · **Posted:** Sun Aug 31, 2008 9:42 pm

kccrd wrote:

I put a little dielectric grease on the belt in 4 to 5 spots across the ribs of the belt smeared it around a little and all chirping went completely away. A service manager a my local jeep dealer told me to do it. Worked great but I just changed the alternator pulley and cleaned all the other idler pulleys and put some high temp grease in the middle shaft to make sure they ran smooth. Give the grease a try does not cost much.

I put a new belt on and greased all the pulleys as well as the spring on the tensioner. I didn't think it would last long but I thought if the noise stopped I would at least know its a pulley. The noise was still there, just not as bad. It is still better than it was and its been a few months now. I just think my problem has gotta be the pulley or the AC clutch. I will try replacing the pulley first since its cheaper.

AC / pulleys/ serp-belt noise?

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