Serpentine Belt Squeal (Bad Alternator Pulley?)

[Jflow23]

My serpentine belt squeals really bad on startup and is becoming more regular and lasting longer. I can sometimes hear a split second squeal when my SAI kicks in (it roars like a jet engine and also needs to be replaced) and I can sometimes induce the squeal when the car is cold and I turn the wheel. After it squeals for about 5-15 seconds it goes away and does not comeback.

History:

I have tried changing belts and tensioners. Original tensioner had a bad wobble on idle, but never made a squeal. I swapped it for a Meyle unit and Continental serpentine belt when I did my timing belt 2 months ago. Wobble went away, but the car serpentine belt would occasionally squeal for about 5 seconds on a few starts.

This morning:
I swapped in an OEM belt, because I read in a thread that the OEM can be a tad shorter. I have the right belt based (shorter of the two) based on VIN. I also turned all the accessories by hand, they seem ok...no binding or grinding. OEM belt still squealed, and I threw another tensioner at the problem and it seemed to be OK...

This evening:
The squeal was back and lasted longer than a few seconds and I was able to pop the hood and get a good look. I could smell the belt getting hot and immediately turned off the car. It's definitely coming from the serpentine belt, not the timing belt. The alternator pulley was very hot to the touch while the other pulleys were only warm. After it cooled enough to be touched, I gave it a few turns and it turned freely in both directions. Not sure if that is supposed to happen, I understand there is a clutch mechanism in the pulley.

I think the alternator is probably the problem, based on the slippage occurring on the alternator pulley and the squeal when the SAI kicks on. but I was looking for a second opinion and possibly some additional troubleshooting before I dump a few hundred dollars on a new alternator (going full alternator instead of trying to figure out how to replace just the pulley), only to find out something else is the problem.

[diagnosticator]

I agree with you, that the alternator pulley clutch is defective. The pulley clutch is supposed to lock in the driving direction, then free wheel in the opposite direction, to smooth out the torsional vibrations from the crankshaft transmitted into the accessory driven components. The fact that the alt pulley is hot, is evidence the clutch is slipping and not locking properly. Replacing the pulley requires special tools, and considering the alternator has more than an few miles on it, the best solution is by replacing the alternator.

[Jflow23]

Thanks Diagnosticator, I was hoping you would chime in.

[RENOxDECEPTION]

http://www.youtube.com/watch?v=fyosuYbPxr4

[Jflow23]

http://www.youtube.com/watch?v=fyosuYbPxr4

Thanks for the link...just checked, pulley does not slip in the reverse direction.

[deadend9009]

What about the power steering pump? I have the same issue. I thought clutched alternator pulleys were only found on diesel engines. I'll have to look at mine, I guess!

[Jflow23]

What about the power steering pump? I have the same issue. I thought clutched alternator pulleys were only found on diesel engines. I'll have to look at mine, I guess!

It definitely has a clutch pulley...and mine is completely seized. I pulled the alternator this morning and verified. The squeal was unbearable this morning, it would not stop. I matched part numbers to this INA pulley Click. No local stores stock Audi parts in Nebraska so I and am waiting on a replacement...should be in tomorrow.

It's was pretty easy to check the pulley with the alternator installed. I just loosened the tensioner with an 18mm wrench and slipped the belt off of the alternator and carefully let it slide down and rest on the PS pulley. I blocked the alternator vanes with a screw driver and attempted to spin the pulley in reverse...no luck. The pulley is supposed to slip in the reverse direction when the vanes are blocked. I hope this fixes my problem and there are no additional issues.

[RENOxDECEPTION]

Cheaper?

Tool

[Jflow23]

Cheaper?

Tool

Thanks for the links, but I bought a remanufactured alternator from a local store for ~$200. The heat and the smell of the belt made me think twice about waiting...and the sound is awful and embarrassing. I don't have an extra vehicle so this needs to be fixed ASAP. Wife already hates audi maintenance, she is on me to get a new car. Her carting me around for a week would be probably not be fun. For some reason I have this strange love/hate relationship with this car and I'm not ready to let go.

[RENOxDECEPTION]

Lol

[Jflow23]

Update:
New alternator went in today with functioning clutch pulley. No dice...super loud squeals continued.

I swapped in another tensioner, all quiet. I'll report back after a few cold starts. The video posted by RENO mentioned that a failed pulley will kill a tensioner...that statement would appear to be fact. The dead tensioner only had ~1K on it, before giving up.

[gtsingh91]

Not to thread jack, but it's related to the serpentine belt. Anybody get an annoying sound from the serpentine belt on a cold start? it's not a squeal but almost like it touching something. After driving down the block though, it goes away. I don't really know how to explain it. The timing belt kit from ECS included a serpentine belt with a tensioner and as far as I know, that was changed out by a local shop about 5k miles ago.

[RENOxDECEPTION]

Not to thread jack, but it's related to the serpentine belt. Anybody get an annoying sound from the serpentine belt on a cold start? it's not a squeal but almost like it touching something. After driving down the block though, it goes away. I don't really know how to explain it. The timing belt kit from ECS included a serpentine belt with a tensioner and as far as I know, that was changed out by a local shop about 5k miles ago.

I think I know exactly what you're talking about. It sounds different in the car than under the hood. Made a video, the sound goes away at 0:14 and then runs normal:



Order of sounds:


0:00 -Startup

0:02-0:04 -Cam Chain Tensioner Gaining Oil Pressure

0:05-0:14 -???

0:14 -Normal

[B6_Dolphin]

Anybody get an annoying sound from the serpentine belt on a cold start? it's not a squeal but almost like it touching something. After driving down the block though, it goes away. I don't really know how to explain it.

Does the sound go away with the engine warm? I have a similar sound after a cold start, and it is a slow cyclic "one blip" sound, not like the above post, so it is something in the accessory drive (belt/bearing, etc.). The belt and tensioner is new, as well as the timing belt/water pump/tensioners.

[SlickFix]

when my SAI kicks in (it roars like a jet engine and also needs to be replaced)

Have you checked the hose that connects the SAI pump to the air filter box? Mine was roaring and it turned out to be that the hose was simply not plugged into the air filter box completely.

[gtsingh91]

Does the sound go away with the engine warm? I have a similar sound after a cold start, and it is a slow cyclic "one blip" sound, not like the above post, so it is something in the accessory drive (belt/bearing, etc.). The belt and tensioner is new, as well as the timing belt/water pump/tensioners.

That's what I'm talking about. It goes way when the engine is warm. Same sound.

[ECS Tuning-Audi]

I was going to mention that it could be the tensioner but looks like its already been said. Sometimes just an old belt will squeal. Easiest cheapest way to try to correct this is throw a new tensioner and belt on.

We have service kits below that include everything you need to perform the replacement.

Click HERE to order or for more information


Jason

[Charles.waite]

Keep in mind, everyone, there is a VIN split for the Accessory belt. The early belts are 1590mm long and the late belts are 1570mm long.

I have no idea why this is, could be due to a slightly larger pulley on a different alternator/PS Pump revision, but if the belt is too loose because you have the wrong one, its could easily squeal.

My tensioner used to bounce like crazy. I recently replaced the tensioner AND the idler roller thats below the tensioner. Its a good thing I did because the idler bearings were crunchy and likely wouldn't have lasted through a whole 'nother belt change interval. After the replacements, the belt hums along relatively smoothly.

[Jflow23]

Update:
A few cold starts later and it's as loud as ever, but quiets down after the SAI turns off. Occasionally when my SAI cycles the belt squeals. Could a dying SAI place too much load on the alternator? That doesn't seem realistic.

PS resevoir was slightly below max, topped that off for good measure. I've applied pressure at the tensioner to try to increase belt tension when the noise is active and still slips on a component. Turning the AC off while the noise is going does not stop it. Turning the wheel immediately after the noise has settled will make it start again. The alternator pulley still seems to get hotter than the others, perhaps the alternator is misaligned?

I am going to try cleaning the pulleys with brake cleaner to ensure there is no dirt or oil in the tracks causing the belt to slip and attempt to measure pulley alignment accross all the components. I really don't want to pull the front end off to try to align components that should just fit. Opent to any other suggestions. I'm going to give the Continental belt another shot, it seems a hair shorter than the OEM one.

Anybody have a 1.8t PS pump DIY? Not sure that is the problem, but curious to know what I'm in for if I have to swap pumps.

[Charles.waite]

What is the battery voltage while idling? I believe it should be close to 14V. Anything around 13.5 or less points to a dying alternator.

I'm not sure if they can be rebuilt but I vaguely remember seeing a DIY on replacing the brushes in the alternator.

[RENOxDECEPTION]

In reference to the video I posted above, today my car showed the first signs of it being a belt squeal, only lasted 5 seconds but it was long enough to know for sure. I already checked my alternator pulley, its perfect. my guess is on the tensioner (which I noticed had a slightly worn bearing when I did my timing belt last), and also I have a slightly broken/unbalanced fan.

[diagnosticator]

Whatever the electrical load is on the alternator, the belt should never slip on the pulley. If the pulley is heating up, then there is not enough tension in the belt drive. The alternator output will max out before the belt slips on the alt drive pulley by design. An electric motor will pull the amps from the power source according to how much load is on the motor. If the motor is seizing or overloaded, the current draw will exceed the cooling capability of the motor windings, and the motor will eventually burn out. The capacity of a belt drive to transmit power, depends on the belt speed, and the width and belt tension. If the belt is not tensioned enough it will slip. If the applied load is higher than the designed maximum capacity, the belt will slip, If the belt speed is reduced by a dragging driven load, the belt will begin to slip when the belt speed decreases with full load applied.

[Jflow23]

Whatever the electrical load is on the alternator, the belt should never slip on the pulley. If the pulley is heating up, then there is not enough tension in the belt drive. The alternator output will max out before the belt slips on the alt drive pulley by design. An electric motor will pull the amps from the power source according to how much load is on the motor. If the motor is seizing or overloaded, the current draw will exceed the cooling capability of the motor windings, and the motor will eventually burn out. The capacity of a belt drive to transmit power, depends on the belt speed, and the width and belt tension. If the belt is not tensioned enough it will slip. If the applied load is higher than the designed maximum capacity, the belt will slip, If the belt speed is reduced by a dragging driven load, the belt will begin to slip when the belt speed decreases with full load applied.

I understand you, my thinking is that I need more friction on the belt because I have been unable to get there with tension alone. I cleaned all the pulleys with brake cleaner, still squealed. The alternator pulley felt like glass to the touch, so I decided to gently roughen it up with a wire brush to try to increase the friction coefficient between the belt and the pulley. It has appeared to work for now...I need a few more successful cold starts to call it good.

[diagnosticator]

I understand you, my thinking is that I need more friction on the belt because I have been unable to get there with tension alone. I cleaned all the pulleys with brake cleaner, still squealed. The alternator pulley felt like glass to the touch, so I decided to gently roughen it up with a wire brush to try to increase the friction coefficient between the belt and the pulley. It has appeared to work for now...I need a few more successful cold starts to call it good.

Yes, the coefficient of friction is a key aspect as well. With a new belt, it is generally assumed that the friction is a fixed value and is sufficient according to the drive design. While roughening up the alt. pulley was good thinking, the roughness factor will disappear as the pulley gets polished by the belt after the drive is operated for awhile.

[Jflow23]

Yes, the coefficient of friction is a key aspect as well. With a new belt, it is generally assumed that the friction is a fixed value and is sufficient according to the drive design. While roughening up the alt. pulley was good thinking, the roughness factor will disappear as the pulley gets polished by the belt after the drive is operated for awhile.

It's working...for now. That new pulley was very slick, I don't think a belt is capable of achieving that level of polish. The OEM pulley is black anodized and not nearly as slick (especially within the grooves) as this polished aftermarket pulley. I'm hopeful that the problem will not return. Thanks for your help along the way.

[diagnosticator]

It's working...for now. That new pulley was very slick, I don't think a belt is capable of achieving that level of polish. The OEM pulley is black anodized and not nearly as slick (especially within the grooves) as this polished aftermarket pulley. I'm hopeful that the problem will not return. Thanks for your help along the way.

..