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Is it the decoupler or the alternator bearings?

67K views 36 replies 18 participants last post by  scotter5 
#1 ·
In the last week or so of driving, I've noticed a low, rhythmic, ruh...ruh...ruh.. noise coming from the drivebelt side of the engine when the engine is under load - A/C compressor, putting it in gear, running quite a few accessories, etc.

I've scoped the source of the noise (long screwdriver to the head-style) down to the alternator assembly, but I'm wondering if there's a test that can be done that will tell me whether I should just replace the decoupler pulley OR whether the bearings in the alternator itself are on the way out, and I just need to swap the whole thing.

Any ideas?

Nate
 
G
#2 ·
Two of the three Chrysler minivans we owned before our current one had to have new alternators at about the same mileage as yours (the fourth didn't make it that far due to accident). I imagine someone here can answer your direct question about which component to fix, but I'm wondering if sometime soon yet another will fail on it and you will probably end up replacing the entire assembly anyway. Just my two cents worth (and even at that the advice is overpriced!), but maybe it would be worthwhile to replace the alternator now and be done with it. -Ken
 
#3 ·
I'd say it's the decoupler making that sound. My 03 has been making that sound for a while now. I took the cap off of the decoupler and sprayed a little PB blaster in there, it helped for a little bit, but not long. I'm just going to wait until it completely breaks or the alternator quits charging.
 
#5 ·
My alternator started to make a whirring noise at about 160,000 kms (100,000 miles). Replaced it and still have the old decoupler on there.
If an alternator bearing is bad, I would expect a whirring sound. Put your hand on the alternator and see if you can feel roughness or vibration. If working properly, it should be running smoothly.
A Mechanic's stethoscope may help "pin point" the noise.
The noise you describe sounds pulley related. Any particular noise at shut down or startup? Thats when the decoupler comes into play.
 
#6 ·
There's no particularly strange noise at shut down or startup. I would compare the noise as a diesel-like rumble, very rhythmic, coming from the alternator, only when the engine is under load. I may go take another listen to startup/shutdown noises later today and update if I hear anything different.

Nate
 
#7 ·
Mine has the diesel like noise as well but only at idle, plus the whirrr spin down when I shut it off. (I might be due for both alternator and pulley) Does your noise go away as soon as you increase RPM? Do your lights flicker or do you notice a dim of lights and fan when coming to a stop?
 
#9 ·
The noise goes away as I increase RPM, and I do not notice any dimming of lights or fan when I slow down RPM.

At this point, I've got one of the Miller tools on its way to me and I'm planning to swap out the pulley some time in the next couple weeks (God willing it doesn't fail catastrophically before then). I've got a vice that I need to mount to some lumber as well before I do the job. Haynes says to remove the alternator by way of moving/removing the oil dipstick tube, but I've read in a few threads on here that going via removal of the EGR valve is easier. It looks to me like the space I'd open up by removing the EGR valve would be larger - is that the way to go, Haynes be darned?

Nate
 
#8 ·
It is the pulley. Autozone or advance auto parts do not sell the pulley just the alternator. Napa sells the pulley for $80 plus have to find or purchase special tool to remove and install. I ended up buying at advance auto parts for I think around $160 with a lifetime warranty. Once alternator was replaced, noise went away and wife was very happy and not embarrassed to drive kids to school anymore. lol
 
#10 ·
Nate,

I had the pulley noise about a month ago (I replaced my alternator given my location, the apparent lack of a pulley tool locally, and the cost of said tool).

Possibly out of complete ignorance, I removed the alternator without removing the dipstick or EGR valve. The "lower front" bolt was a bit tricky to remove, however, patience and a open ended wrench served me quite well. :thumb:

Honestly, it was one of the easiest DIY jobs I've had to do - I hope you have the same luck!

Cheers,
radman
 
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#12 ·
Radman,

I hope it goes as well for me as it did for you. Looking at the positioning of the parts, I guess my mind's eye just can't see the alternator being able to sneak out of it's place without running into either the EGR valve or the oil dipstick tube. I'm assuming you were able to slide it through in between the dipstick tube and the cooling fans, then?

I won't be doing the job for a number of days, as the tool is still en route and I've got to find a spare half day (the minimum that I'd tell my wife it would take to do any auto service work, otherwise I've found trouble ensues).

Nate
 
#11 ·
BTW, no worries of catastrophic failure in the near term methinks. I let mine go for a few weeks (hoping to snag a cheap Miller tool on eBay). I read somewhere some drove for a year with the noise!!
 
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#17 ·
That may have been me. My van has been making that 'rawr rawr rawr' sound for well over a year and about 15,000 miles. The sound has not gotten any worse (or better), and as I said I'm driving it till it breaks.
 
#13 ·
Hi Nate,
Indeed, I hope it goes well. If I recall correctly, I sort of "rotated" the alternator (such that the pulley was facing up) when I took it out.

I removed mine twice (after I had it out the first time, I was bothered because I realized the pulley on the new one looked a bit different from the OEM ... so I reinstalled it and consulted this forum!). No black magic or voodoo req'd for removal either time.

I wonder if your van has the same "configuration" as mine? Attached is a pic of the alternator on my 2003, when looking down at it.

Hope it helps ... and do let us know how things go!
radman
 

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#15 ·
No EGR valve at the end of the head in that picture. I believe I can see the blank plate where the EGR vale goes.
Mine doesnt have an EGR valve either. We're lucky.
 
#14 ·
Radman, I don't see the same placement of the EGR in your picture as mine (and perhaps nate). Our EGR is right at the very end of the head, right beside that alternator. Mine has been noisy for at least a year. Hopefully it will hold out until the weather warms up when it would be much more comfortable to replace.
 
#18 ·
Thanks jgbat, it's better to have someone come forward, rather than the weak "I heard about someone who ..... etc." ;-)

Nate, so the absence of the EGR valve indeed explains the difference in apparent difficulty. Let us know how you approach the repair and how the results are ... that will help "the next guy".

If Jeepman and I don't have the valve, is this due to a Canada/US model difference?

Cheers,
radman
 
#19 ·
Your welcome. And my 03 does not have an EGR valve either.
 
#20 ·
Mine too has made this noise for well over a year (maybe even two) without it getting worse (knock on wood). As I also get the spin down noise out of the pulley, I may replace both once the warm weather comes back. I will most likely pull the EGR to make things easier.
 
#22 ·
Well, the job is done now and here's what I learned about removing/replacing the alternator as far as room to operate goes:

Per Haynes and others, I attempted to remove the oil dipstick tube. It's held on by one bolt to the block and a plastic "christmas tree" type of cable tie on the main wiring harness. With those two connections undone, my dipstick tube would not (and I didn't want to brute force it) come up and out of the oil pan, but I was able to lean on and wiggle the dipstick tube around some, giving me some room. I tried a lot of different positions and rotations and strategies to get the alternator out through the space between the dipstick tube and the electric cooling fans, but it would not come. I'm thinking perhaps an AutoCAD program could have helped me devise a successful strategy, but I don't know.

From there, I just took off the EGR valve carefully. Disconnected the electrical fitting first, then loosened and removed the 2 bolts that fasten the EGR valve to the EGR tube first (8mm head), then the 2 bolts that fasten the EGR valve to the block right by the exhaust valve for cylinder 2 (10 mm head). That opened plenty of space to remove and re-install the alternator.

Putting things back together, I found that it was easier to re-install the EGR valve completely before I tightened down the alternator bolts because otherwise, the alternator makes it tough to get a 10mm socket squarely on the lower bolt that holds the EGR valve to the block. For my van, I tightened all 4 EGR valve bolts to 115 inch lbs torque (Haynes said b/w 90 - 125 inch lbs). I was gentle with the gaskets on the way out, and kept them in the same orientation and re-used them on the way back in.

If I have to replace the alternator again, I plan on loosening the dipstick tube by removing the bolt (but not unplugging the plastic christmas tree fitting to the wire harness) to give me room to swing a wrench on the front alternator bolt AS WELL AS removing the EGR valve assembly.

Nate
 
#23 ·
Careful before you replace stuff!

I had the exact same problem... got up under there and listened intently, decided it was the pully tensioner... replaced for $50 at autozone.... didn't help. Then took it to the "Pro's" at PepBoys so they could at least pinpoint the noise. For $75, they told me it was the alternator pully... $210 later, I replaced the alternator. yes, the shaft of the alternator was bent... but the noise came back. I have narrowed it down to the A/C clutch, since it doesn't happen unless the A/C is on, low RPM. For now, the wife can live with it...
 
#24 ·
Help is here.

Ok,

In my professional opinion this is what I think may of happened.

You misdiagnosed the noise as a tensioner noise. (very common mistake)
You replaced the tensioner and confirmed this.
Pep boys correctly diagnosed the problem as the decoupler pulley.
You replaced the entire alternator but it may of had the wrong type of decoupler on it.
Ergo the problem is still there.

You don't have to live with this annoying noise (and I know the exact noise you are talking about!) You can relpace just the decoupler pulley with the correct one. You can go to www.decouplerpulley.com and get more info. If you still need help you can email me directly at allen.steadman@litens.com. I would be happy to help.

hope this helps.

AL
 
#26 ·
Al,

Do you know if it is common to experience tremendous difficulty in removing the original decoupler pulley from the alternator. That's where my job turned into a complete alternator swap, as I followed written (and video) instructions, ended up cranking the torque WAY up, and still was unable to break the old pulley loose. The 10mm heat bolt to the shaft rounded off first, and that was with a high quality 6-point socket head on it. So far, my new alternator has been quiet (2 weeks, 600 miles) though.
Ok,

In my professional opinion this is what I think may of happened.

You misdiagnosed the noise as a tensioner noise. (very common mistake)
You replaced the tensioner and confirmed this.
Pep boys correctly diagnosed the problem as the decoupler pulley.
You replaced the entire alternator but it may of had the wrong type of decoupler on it.
Ergo the problem is still there.

You don't have to live with this annoying noise (and I know the exact noise you are talking about!) You can relpace just the decoupler pulley with the correct one. You can go to www.decouplerpulley.com and get more info. If you still need help you can email me directly at allen.steadman@litens.com. I would be happy to help.

hope this helps.

AL
 
#25 ·
I have been chasing this "rough bearing" sound on a 2005 T/C that I bought a month ago for the last week.

I had a 1 month warranty on the van, and the dealer did have it looked at for me. They did replace the idler pulley and told me that was the issue. Wife picked it up and told me it sounded like she was "driving a tank". I was on the road, so I investigated it when I got home. Still noisy!

So... I called the dealer again and they told me to bring it back to the place they had fix it the first time. When I got there, the tech told me about the decoupler pulley and told me he had told the dealer about this. (Dealer neglected to tell me that part.) That was the first time I have ever heard of such a thing!

I came home and did the search on my favorite Chryser Mini Van forum :biggrin: and found this thread! Thank you all for cluing me in... especially to Al Steadman for the link he provided that had a great video as to why the decoupler is there!

Now I just have to figure out how to convince the Mrs. that it is not a failure waiting to happen, and that nobody else will notice the noise coming from her nice, new, "ghetto cruising tank!"
 
#27 ·
I have never had a problem with the correct special tools and turning the correct way (shaft goes counterclockwise when holding the OAD shaft). See video on youtube. http://www.youtube.com/watch?v=ZLFAe3DerqA&feature=related

Note: If someone has replaced it before and screwed up the alternator threads then you will have an issue.

Hope this helps.

Your pal AL
 
#28 ·
I am still a newbie on the forum but I had to learn the hard way on the decoupler pulley problem. I had the altenator rebuilt and a conventional pulley was replaced on it. When I put it back on van, the noise was cut in half. It would still make noise under a heavy load so I read all about it on here. Thanks for the help on this. I ordered the correct decoupler pulley and all was fixed. Acceleration, shifting, power steering, and noise was 100% better.
 
#29 ·
This is great information.

Is it a good idea to install a new or rebuilt alternator with a new decoupler pulley? If the alternator charges assume just install new pulley? I assume you have to remove the alternator to install a new pulley? Where is the cheapest place to buy the removal tool?Thanks
 
#31 ·
#32 ·
I've been driving my 2001 T&C since I hit 91k miles on it (I now have 145k) and when turning the car off, my wife thinks it's funny the car "purrs" are you with the "Rawrrrrrrrrrrrr" noise. During operation there is no unexpected noise from the alternator. I was told by the dealer that the noise is the decoupler pulley which was installed to stop a "clicking noise" from occurring during normal drive and shut off. The mechanic did warn me that in another 100k miles it might wear out the alternator bearings. So I guess I'll replace this in another 4 years if I still own her then.

The fact this is the only AWD van I can find I can lay a full 4x8 sheet of lumber in when the seats are out (or drywall) means I'll likely keep her on the road as long as I can...I like my Truck/Minivan.
 
#33 ·
i have watched that video, and i havnt got that sound. Mine is like a whuuurrr, and the pitch gets higher when i rev it, ( in or out of gear ) Now mine is a 2003 grand voyager, and has 184000 miles. I think maybe ill upload a video of the sound later, and see if any one else has the problem.


bradleigh
 
#35 ·
Hi All,

I'll jump in with my alternator decoupler experience. It took me a little bit to diagnose the problem and installed a new idler and tensioner first. I pulled the alternator off and brought it to a local starter/alternator repair shop. He pulled it apart for me and showed me the coiled spring inside and it was rusty - which is why most fail. Anyway, he replaced the decoupler with a solid pulley that he had machined and in stock...since he does alot of these. $35 was the final bill. I asked him if I needed to rebuild the alternator. He said no - its a Denso and will run to 200K. If anyone is interested - I can give you the contact info and I'm sure he would mail you a pulley.

Also, as far as removing and replacing. Take the alternator out of the bottom. Loosen the motor mount on the left side and left your engine down with a jack under your motor. My alternator is quiet...now I'm getting a noise from my ac pump...!
 
#36 ·
I just went back and read the entire post. Looks like I gave bad advice in my last post...and it is too late to edit it :(. I had the solid pulley installed on the alternator shops recommendation when I started getting the noise. But the noise has come back and I was seriously worried that it is the ac pump...since it is the worst when the ac is on. So for 8 months the noise has been gone and recently come back. Hopefully, I didn't damage anything.
 
#37 ·
Don't blame yourself. You didn't do anything to damage it--if the noise went away, great. I can't see why you would have done anything if the noise went after replacing the pulley. That sounds like it was alt. pulley, so you did good, when you replaced it. This maybe a different sound.

MOst likely not the compressor pump-could be the the coil/pulley on it---feel the a/c lines under hood--are they cold--if so--most likely not compressor but pulley/coil.
 
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