TDI Whistle Noise: Causes & Fixes

Hello everyone!

Vehicle: Volkswagen Lupo 1.4 TDI PD, engine code AMF.

'Recently, I've been experiencing the following problem with my Lupo:'
During the ride, a whistling sound (or a high-pitched howling) occurs.
The noise isn't always present. Sometimes it appears immediately after starting the vehicle, and other times it doesn't occur until half an hour later (and it always seems to happen suddenly).
It's usually heard when I, for example, accelerate quickly from a town at 50 km/h in 3rd gear - and then it remains audible, regardless of the gear.
Sometimes, as I said, it's not even there at first, and then it appears suddenly.
The error database mentions wind noise coming from the mirrors, but I covered them with tape and the noise was still present (so that's not the cause).

If there's a whistling sound due to the wind, that whistling should be constantly audible from the device.

How can I pinpoint the source of this damn noise?
Could it be related to the pump-injector system (do they start whistling shortly before they fail?)?
Could it be the charger?

I mentioned it to the service department at the car dealership - the master technician heard it (he removed the antenna because he suspected wind noise). Unfortunately, it was raining, so it wasn't easy to pinpoint the source of the noise (he found a good excuse).

Before I go back to the car dealership, I wanted to check it out myself or see if anyone else knows about it.

I would be very grateful for any help.

Best regards, D.

Hello,
The problem could be a loose piece of adhesive film (e.g., a stone chip guard on the rocker panel) that is then 'vibrating' in the wind.
Best regards, Jens.

The 3-liter Lupo is also known to have whistling fuel preheating valves on the diesel filter. Apparently, this sound is even more noticeable when using RME (rapeseed methyl ester).
Otherwise, you need to describe in more detail whether the whistling occurs only when the clutch is engaged, or whether it's the same whether the clutch is engaged or disengaged.

Best regards,
Dirk.

In my opinion, Brezelmann's hypothesis seems to apply only at low engine speeds, when running on rapeseed methyl ester (RME), and sometimes also when running on other biofuels (PÖL), and more often when the engine is cold.
This sound typically occurs more frequently at low loads and during idling.
The whistling sound during acceleration is likely only occurring under heavy load (3rd gear or higher), at engine speeds well above 2000 RPM, and with a lot of throttle applied.
"The noise is definitely related to the turbocharger or the pressure hoses. In my case, it appeared around 80,000 km. No error codes could be found. When I had to rebuild the turbocharger, the noise disappeared. Since new hose connections were made during the rebuild (and the EGR valve was removed and cleaned), I can't say for sure what the exact source of the leak was. It's a very minor leak... and as long as it doesn't lead to increased soot or power loss, I would ignore it and hope to randomly find the source of the problem."

Regards,

Olaf.