Alternator Belt Squeal: Causes & Fixes

Hello dear diesel mechanic community.

I'm new here, but I've been following the discussions in the forum for quite some time. I think it's great that there are so many professionals among you who are willing to help others in need!
I'm also somewhat technically inclined myself, and I've usually been able to solve problems using my own knowledge and skills. However, for the following problem, I need some suggestions from professionals. Please excuse me that the text is a bit longer...

Regarding my problem.

I bought a Golf III TDI, 90 horsepower, manufactured in April 1997, with 64,000 km, and currently it has 126,000 km.

Since I bought it, the humming sound from the flat ribbed belt of the alternator has been bothering me. This humming and vibration are caused by the tensioner element in the range of 1200 to 1500 revolutions per minute. At this speed, you can see that the tensioner roller rises significantly, and the belt starts to swing, which is why there is humming and vibration.
VW also admits that this design has a major flaw, but what good does that do me now???
To my knowledge, the 1.9 D and 1.9 TD engines, at least in the Golf III, do not have a tensioner, which means there are no vibrations or humming. However, this likely puts more strain on the alternator bearings. Consequently, tensioners were introduced in the TDI engines, which use a lever and tensioner pulley to apply constant pressure to the belt. This reduces stress on the bearings and, more importantly (at least in theory), eliminates the need for regular maintenance tasks like adjusting the belt tension every 15,000 km.
Everything is fine and good, but they installed an undamped spring element that is prone to oscillation due to its rapid degradation.
It wasn't until models like the Passat and Golf 4 that an additional vibration damper was installed, or the entire design was changed. Some people don't have any problems with this, while those like me have to replace the belt and tensioner every 20,000 kilometers just to enjoy smooth engine operation.
I had the entire set replaced once by a mechanic (at 65,000 km) and have replaced it myself twice (at 90,000 km and 115,000 km) – each time costing around 90 euros. I'm slowly getting fed up with it, and my wallet is getting empty.

VW employees have admitted that it is likely a design flaw, and that there is supposedly an upgrade kit available to fix it, but so far, they haven't installed any of them! Furthermore, they haven't disclosed what components the upgrade kit consists of or what it will cost, which is typical of VW's communication...

Here are my thoughts and questions for you:

I would like to remove the tensioner and the entire associated assembly and replace it with a flat ribbed belt, specifically a 1.9 TD belt (6 PK 751). I want to adjust the belt tension using the alternator, like in the old days. Unfortunately, the alternator and its bracket are not designed for this. Does anyone have any experience with this?
Are there perhaps any other ways to permanently eliminate this problem?
Can a vibration damper, for example from a VW Transporter, be retrofitted?

Or could it be due to an incorrectly set injection timing? I read a thread in this forum about vibrations up to 2000 RPM caused by incorrect injection timing.

I look forward to your suggestions and experiences.

Thank you.

Georg-TDI wrote:

Or could it be due to an incorrectly set injection timing? I read a thread in this forum about vibrations up to 2000 RPM caused by incorrect injection timing.

If the roller and belt are starting to wobble, it's unlikely to be due to the start of the spraying process – at least, that would be something completely new for us.

So, attack the issue at its design flaw, as the chances of success are quite high (I cannot provide you with details).

P.S.:
Could you please post the link to the thread about vibrations up to 2000 RPM caused by incorrect injection timing?

Hi.


How much does the needle swing (in cm)? Mine swung 1-2 cm with the old element, but almost 0 cm with the new one.

I just removed my span element yesterday (it took about 5 minutes).


The spring element (now 2 years old) is sticking! It almost hovers in the air when you lift it off the strap and let it go.

Perhaps the ridges are more pronounced on your belt, causing it to hit harder.

Here are some photos of my crafting projects:

http://people.freenet.de/golf-schrauber/Spannrolle/Spannrolle_1Z.html

Hi there dieselmartin,

The tensioner pulley hardly oscillates with the new tensioner, but it can oscillate up to 2 cm, just like in your case. When I had to replace the tensioner twice myself and ordered new ones from VW, the first thing the VW employee said was: 'Is your tensioner locked in a certain position? Is it difficult to move? That's a typical issue...'
However, I have never observed such a pattern with my older tension elements. I also always checked and lubricated the play in the sleeves. My current one is only 1.5 years old, and it's perfectly free-moving, but it's already stretched. After just six months with the current tension element, I had to install a slightly shorter flat belt to avoid strong vibrations. The VW technicians, of course, were against it and told me that the increased tension would soon cause bearing damage to the alternator. But that's not the case; the intended tension is lost after just a few months.
It worked well for about six months, but for months now, there has been a strong humming and vibrations again, which are also clearly noticeable from the inside.
Since I drive an automatic car, I often find myself in the RPM range of 1200 to 1800, especially in city traffic, and that's incredibly annoying!
'On the highway, you usually drive at higher RPMs, so this problem doesn't typically occur. Drivers with manual transmissions have fewer issues; they can choose the specific gear and corresponding RPM themselves (unlike me).'

Thank you all for your helpful responses to my problem.

I will soon be sharing my extensive experience, both positive and negative, with biodiesel. (I saw a poll about this on this forum.)