1.9 TDI ATD: Scheppern beim Anfahren | Posts 16+

*fauch*

Now this damn noise is also happening with a cold engine in the first few minutes of operation... So, you start the engine and then realize it's ice, not water, on the windshield, so you get out and scrape it off... and here too, you hear that awful noise. This probably rules out the engine mount as the cause.

Okay, so it seems like the problem is likely with either the V-belts or the timing belt system (specifically, a tensioner or one of the auxiliary components) or with the timing belt itself.

And the latter doesn't necessarily cause me less worry .


I guess I'll probably have to take some time this weekend to remove the belt and check if the problem is with the ribbed accessory belt. Hopefully, that's all it is.

I haven't had a chance to take it apart yet because I'm currently so busy with work that I only get home when it's dark.

I can provide some new details: The noise only occurs when the engine is idling and cold, and only when the generator is under load. In other words: lights off = no noise; lights on = noise.

Therefore, I'm no longer going to rely on the timing belt, as it doesn't directly handle that load in the same way as the ribbed belt itself.

In my opinion, there are two potential culprits: the alternator (although the freewheel clutch was replaced 30,000 km ago), and the ribbed belt tensioner. Both of these components have the same mileage as the car (234,000 km).

What do you think? Removing the belt definitely eliminates the noise, but I'm not sure if it's the generator bearing or the tensioner causing it. Generator bearings should make quieter noises even when idling, and that wouldn't explain the rattling sound during acceleration as the engine speed drops. The tensioner seems more likely to be the culprit for rattling sounds.

Experiment: Apply WD-40 and see if it eliminates the noise?

"You can't really reach the tensioner... at least not without either propping it up and/or breaking all your fingers. And I don't want to mess things up - so if you think it might be the tensioner, then we'll just replace it."

I would first arrest all the suspects one by one, no matter how. There has to be a way to do it. You can always trade them later.

It's clearly a metallic sound - I definitely won't spray anything on the belt, otherwise it might slip and I would have to disassemble everything . I currently depend on the car every day... so my desire to "experiment" with it is relatively low .

While running, occasionally apply silicone spray to the belts and listen for any unusual noises.

Octavia_4x4 wrote:

It's clearly a metallic sound - I definitely won't be spraying anything on the belt, otherwise it might slip and I'd have to disassemble everything I currently depend on the car every day... so my desire to "try things out" is relatively low

.

Don't worry, it won't slip. My strap was 2 years old, and it looked as wrinkled as my grandma.

and the belt itself can make such noises?

Because, it's kind of rattling... imagine a motor cover pressing against the oil pan.

"Rattling," yes, that's not usually caused by a belt. A belt is more likely to cause a squealing or rubbing noise.
Do you perhaps have something like a noise shield directly attached to the oil pan?

The belt is moving; where should it go? Or perhaps you're hearing a vibrational resonance.

Deus Violentia wrote:

The belt is moving, where should it go? Or perhaps you are hearing a vibrational resonance.

The noise is not caused by friction, but rather by the belt making contact with or rubbing against the wheel. This can be due to a defective (too old, incorrect size, or worn) belt, although wear on the wheel itself should rarely occur.

What would happen if the valve in the oil pan came loose and started vibrating at a certain frequency?

That explanation about the throttle lock doesn't explain why the rattling only occurs under generator load.

"As far as I know, the belt was replaced at 180,000 km, so it's only about 2 years old. I had a similar rattling noise on my Ibiza before, and in that case, it was the belt tensioner."

It's definitely metallic; it sounds like a rattling ball bearing, etc.


My 4x4 has the reinforced underbody protection, but I had already completely removed it, including the side panels, for testing purposes.

The noise generally occurs when starting and the engine speed drops, and recently also immediately after starting when it's very cold – and in my opinion, this strongly suggests a bearing problem with the belt tensioner.


EDIT: Regarding the immobilizer issue, I'll definitely see something when I deal with customer service. Also, the oil pan is leaking at the seal, which needs to be removed anyway...

I've already replaced the noisy pulleys on the timing belt tensioner before, meaning I replaced the entire unit.

How about a quick check of the engine by pushing it with your hand?

Yes, I would do that anyway before the final change, but for that, I first need to come home at a time when it's still light outside .

Here's my understanding: The bearing is worn and causing friction – the motor increases resistance, which puts more strain on the belt, the tensioner experiences increased pressure – the bearing causes even more friction. When the light is turned off and the load is removed, the pressure disappears, and the friction stops.

Hopefully, this theory is correct.