TDI Belt Drive Noise: Causes & Solutions

Hello,

I'm experiencing a problem with a noise, and despite extensive searching, I haven't found any solutions yet. Perhaps someone here can offer some help or advice.

Vehicle: VW Golf IV Variant TDI, 1.9 L, 90 hp, approximately 93,000 km (purchased with approximately 82,000 km). Longlife service performed at 83,000 km, timing belt replacement including all pulleys at 90,000 km (by my trusted mechanic = independent automotive master technician).

When I picked up the car after the timing belt replacement, I listened carefully to make sure everything was okay and that nothing was rattling. At around 1600 RPM, I heard a buzzing noise coming from the engine compartment. However, I can't say for sure whether that noise was present before the timing belt replacement; I simply didn't listen for it before the change.

Regarding the noise: it's quite precisely in the range of 1400-1600 RPM, in every gear and also without a gear engaged, regardless of whether the clutch is engaged or not. It actually sounds as if, for example, the timing belt is running a bit rough in that range. As for the volume: when driving in 5th gear at 1600 RPM, you can hardly hear it anymore, so it's not particularly loud. It's most noticeable when accelerating in lower gears and when releasing the gas pedal during gear changes. Then the engine speed relatively quickly passes through the 1400-1600 RPM range, and you notice that the engine noise changes noticeably, this rough running noise briefly appears and then disappears.

I went back to the automotive mechanic who replaced the timing belt; he's a good acquaintance of mine. He confirmed the noise, took everything apart again, checked and adjusted everything... but he couldn't find anything.

'Because I was really worried that there might be something wrong with the timing belt, I went to a VW workshop a few days later and explained the problem to the master mechanic. He said it sounded like the timing belt might be too tight or that a pulley was defective, but he would need to take a closer look before he could say anything for sure. Unfortunately, I then mistakenly signed an order form that said 'Noise from belt drive, possibly timing belt.'

The VW workshop spent a few hours working on the car, but couldn't find anything wrong. They replaced the tensioner again (even though it was already new, but you do what you can when you don't have a solution). When I picked up the car, the noise was still there.

Regardless of the fact that this useless action cost another 300 euros, I'm starting to wonder if I'm crazy. The noise exists, but no one has a solution for it.

'Does anyone recognize this problem? Could it be related to the timing belt, tension, bearings, or some kind of resonance...? Is there anything that can be done about it? Or should I just buy earplugs? I would really appreciate any tips. The noise isn't loud, but it's there, and once you notice it, it becomes very annoying.'

I've been thinking a lot about this over the past few days, and I'm now wondering if it's actually the belt drive, or if it could be other noises coming from the engine. Could it possibly be related to the long-life oil? I've noticed that the valves make a slight ticking sound when the engine is warm (though it's very quiet), and I'm attributing that to the long-life oil. I'm now wondering if the long-life oil might be harmful to the engine. I've used regular 10W40 oil in my engines for years, and it's always been fine. Now I'm using 0W30 long-life oil, and I'm not entirely comfortable with it. But again, regarding the noise problem: the noise doesn't change with the engine temperature, which would seem to argue against it being an engine noise, right?

Perhaps someone has a tip for me. Thank you very much and best regards.

Klaus.

Sounds are always tricky when it comes to remote diagnosis.

It's not uncommon for a new belt to make noise. The one on the 1st floor was making a loud buzzing sound for a few days. If the rollers and belt tension are okay, there's not much you can do.

Another possible culprit is the serpentine belt. If you reuse it and install it with the wrong direction of rotation, it can sometimes make noise. It's best to remove it and let the engine run briefly.

Otherwise, I can't tell you whether it sounds like a defect or a new timing belt just based on that.

CU Gremlin.

'In my case, a belt is squeaking rhythmically and quite quietly. It's particularly noticeable when idling and at low speeds (especially with the window open and sound reflecting off a nearby wall).'

I'd also like to know if this is a serious problem. However, it would reassure me quite a bit if it's just the serpentine belt. It's not a major issue if the serpentine belt fails and the alternator stops working. The water pump is driven by a timing belt.