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06 Jetta TDI belt tensioner bounce

dbrannon79

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Hey guys,

while my rig is down I have been driving my daughters 06 jetta tdi 1.9l It's been parked for about 6 months since she bought her new toyota so I decided to take the opportunity to stretch the jetta's legs lol. back before we parked it the belt and tensioner had been bouncing and rattling so I had replaced both. that helped to the point that the noise subsided but was still somewhat bouncing around.

Now that I have been driving it around, the perfuse rattle and bounce is back with vengeance! It sounds like it is wanting to puke the belt (maybe it doesn't like an American made one on a German machine) It only does this while ideling in park and worse while sitting at the light with the AC on, and seems to smooth out just by increasing the rpm from idle (800 or so) to 1k rpm. when I looked at it and shut off the engine, the rattle noise I see is coming from the tensioner stop "banging" on the rest of the tensioner assembly. the belt is maybe 8 months old but has little miles on it due to sitting, so is the tensioner. I would have thought i have driven it long enough that there wouldn't be any rust on the pulley groves, looked and didn't see any.

I have been reading other forums online and they keep talking about the pulley on the alternator being bad! I have looked at the pulley and cant seem to grasp my head around a steel pulley going bad. I have pulled the belt, inspected it and the idler pulley on the tensioner and seem to be ok. the belt only drives the alternator and the AC compressor. no PS pump (electric assist) and WP is timing belt driven. the car has about 290k on the clock and has some serious get up and go power from the pedal lol I found that out be being used to pedals on my rig!!

have any of you guys experienced this or have more knowledge of why others will say the alternator pulley? BTW the alt pulley is threaded on the shaft of the alt and requires some special VW tool to remove. a weird setup I have never seen!!
 

Husker6.5

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Could it be a case of the pulley threads stripping/corroding and the pulley is wobbling eccentrically on the shaft, causing the tensioner to "bounce" around as it adjusts tension on the ever-changing alternator distance/tension.
 

MrMarty51

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I have seen pulleys that looked mighty bad and the belt was smooth running over them.
Remove the belt and give the alternator pulley a turn while holding it. See of there is a rough feel to it, like a bad alternator bearing.
 

dbrannon79

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It just dawned on me that the sound it makes is just like those old Buick FWD motors make when the HB's go out. I will pull the belt and give it all a stern look over tonight if time allows me to, and check the alternator bearings too. one thing that surprised me was when I was looking at it before, I also noticed that the clutch on the ac compressor doesn't have a engagement like we normally see. it's not actually a clutch but just a pulley that turns the compressor full time like on the alternator! there is a valve mounted in the back of the compressor that ether allows freon to flow through the lines or bypasses where the compressor "free wheels" I swear, leave it to the German engineers to throw us Americans for a loop!!
 

dbrannon79

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Welp! I think I just found the problem.... and the reason others are saying the alt pulley...

I dug around the garage for a while (battling mosquitos at the same time) pulled out a special tool set I had to order a few years back that I had to have to remove a starter on one of these Jetta's it's a set of sockets similar to torks but has many more splines! found one that fit into the inner spline on the shaft of the alternator. got my ratchet and channel locks and tugged mighty hard on it to try and do something, what, I didn't know lol and it goes snap!! the pulley starts turning on the shaft. I kept turning and turning and turning.. well this dam thing isn't coming off.

So I try to turn the other way and it latches like a ratchet. I discovered that the alternator pulley has a built in ratcheting function that for what reason I don't know, but the one on this Jetta was seized. I just freed it! cranked it up and it rattled around some then goes all smooth!

so I guess I need to order a pulley from VW. it still does a random bounce here and there sitting at idle, but for the most part is stays smooth. German engineering never ceases to amaze me lol.
 

dbrannon79

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it looks like it's sealed, but I did squirt some wd-40 in the crack where it ratchets trying not to get it on the belt grove. i need to order the splined tool from amazon to actually remove the pulley. here's some photos of the tool and the pulley from amazon. its an 8088 Bosch alternator wrench.

the pulley has a double spline, one on the shaft and another inside the pulley. dam these German engineers!!


1630718298911.png1630718336784.png1630718371461.png
 

MrMarty51

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Hey, I owned a 1984 Audi 5000 Turbo Diesel, I feel your pain!
I got to destroy an Audi V6 from a VW Passat. BIL said 15 links when timing the camshafts, I think it was suppose to be 19 or some such.
Fired it up, rattled, clattered, run rough and began to smoke, baaaad.
It was the most horrible death I ever put a enjun through. I’ll never mess with any thing audi, ever, again.
Welp, his wifey got her way, sort of. She wanted a Cooper mini convertible. He gotter a convertible, Audi of some sort. Not the fastest hotroddy one but close. 😹😹😹
 

JayTheCPA

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German engineering never ceases to amaze me lol.
Don't idolize German approaches *too* much. While engineering can go well, the Accountants have taken them over just like here in the US. And, they are not good at admitting when something is wrong. Been there more than once and watched others go through it.


I dug around the garage for a while (battling mosquitos at the same time)...
Get this stuff:


Works great. Just make sure to regularly re-apply per directions. Available from plenty of sources, so shop for the best price as there is only one supplier.
 

dbrannon79

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for the moment I have still been driving it with the old pulley after I broke it loose. still running much smoother. I may just leave it like this for a while and see what it does, since it's mainly just a spare vehicle.
 

MrMarty51

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for the moment I have still been driving it with the old pulley after I broke it loose. still running much smoother. I may just leave it like this for a while and see what it does, since it's mainly just a spare vehicle.
If not too expensive, might be best to get it replaced. Could cause some catastrophic failure of some other components if it busts loose. 🤷‍♂️
the wifey with that Toyota thing. Got it running after a lot of work and quite a phew dollahs. Then I told her to let is sell the Buick. Nope, she was going to keep that Buick. Well if that Buick is going to be here it is going to be a lot nicer to drive so I dumped some money into that. Then the prom or injectors failed. I still need to take the replies to the guy thats working on it, see if He can determine if the prom had been uprated. But now, there that sets becauseI wanted to sell when it was running good and she wanted to hang onto it.
 

dbrannon79

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Yeah, I will eventually replace it. I may just bite the bullet and do the whole alternator. with it being all OE, just replacing the pulley I may end up needing an alternator for it later! after all my daughter wants to fix it up for one of her brothers to have a first vehicle! as old as it is and high mileage, it still gets 40mpg!! I wish my truck would get half that lol
 

MrMarty51

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Yeah, I will eventually replace it. I may just bite the bullet and do the whole alternator. with it being all OE, just replacing the pulley I may end up needing an alternator for it later! after all my daughter wants to fix it up for one of her brothers to have a first vehicle! as old as it is and high mileage, it still gets 40mpg!! I wish my truck would get half that lol
Thats a good plan. Whut a better way to recycle a older vehicle than to pass it on down. 👍
 

dbrannon79

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Well, it seems the pulley is gonna fail at some point soon, still haven't ordered anything for it yet. pocket book is still in pain from ordering all the parts for my truck! I heard some squalling from under the hood on the Jetta today, as soon as the squalling stopped I noticed the headlights flicker. keeping my fingers crossed it will last another day for a trip to and from work tomorrow. The last package with my water pump and fan controller should arrive tomorrow evening :D

I managed to pickup a 5 gallon clear DEF tank with a sending unit today that I can use for my future water mist project on the truck. it's slender enough to fit between the side of the tool box / aux fuel tank and the inside of the bed. I think 5 gallons should be good for about a 10 hour trip if using a 1/2 gallon per hour nozzle. still more research to do but I think the recommended nozzle size uses less per hour of water. the sending unit even has ports for engine coolant to flow through to keep from freezing, but I'll proprable never use that in south Texas heat!!
 

Husker6.5

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If you make it an on-demand system, based off of boost pressure, you'll find that your consumption of WMI fluid will go down substantially compared to a constant-on system that uses fluid when you don't really need it and it basically does no good (like steady-state cruising).
 

dbrannon79

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If you make it an on-demand system, based off of boost pressure, you'll find that your consumption of WMI fluid will go down substantially compared to a constant-on system that uses fluid when you don't really need it and it basically does no good (like steady-state cruising).
I do plan to have a pressure sensor plumbed in for it to react according to how much boost there is . it's going to be mainly for cooling down IAT's and EGT's but I've heard others tell me depending on how fine tuned it is I might see a little more power and fuel mileage.

Only time and experience will tell. also why I'm not spending very much in this project, I don't want it to be a waste of money. repurposing used stuff where I can lol :)

I know in town driving, it won't help much but for trips and towing, it's a plus. I've heard others using 15+ gallon tanks for this but they also run overkill amounts of fluid through it, that I don't need! I also thought about having a second water line to maybe a washer pump and have a couple of mist sprayers for a quick fast cool down on the ac system and maybe on the cab when it's been sitting out in the HOT sun all day! I can tell ya it's a booger getting into a hot cab that's been sitting in a paved parking lot in the July /August heat !!!
 

Jaryd

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I do plan to have a pressure sensor plumbed in for it to react according to how much boost there is . it's going to be mainly for cooling down IAT's and EGT's but I've heard others tell me depending on how fine tuned it is I might see a little more power and fuel mileage.

Only time and experience will tell. also why I'm not spending very much in this project, I don't want it to be a waste of money. repurposing used stuff where I can lol :)

I know in town driving, it won't help much but for trips and towing, it's a plus. I've heard others using 15+ gallon tanks for this but they also run overkill amounts of fluid through it, that I don't need! I also thought about having a second water line to maybe a washer pump and have a couple of mist sprayers for a quick fast cool down on the ac system and maybe on the cab when it's been sitting out in the HOT sun all day! I can tell ya it's a booger getting into a hot cab that's been sitting in a paved parking lot in the July /August heat !!!
Please do a detailed write up on here when you do this
 
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