Opel Cosa 1.7DTI: Whining/Whistling Noise Under Load?

Hello everyone,

The time of open windows has arrived, and with it, a period of engine noises unlike anything heard before.

'In addition to the normal turbo whistle, I've recently started hearing a strange squeaking/whirring sound under load. It's similar to a grasshopper, but it's a constant tone that occurs when the accelerator pedal is pressed about three-quarters to fully.'

It doesn't happen in first gear, regardless of whether I accelerate slowly or quickly.

'It starts happening from the second gear onwards, for example, when I press the accelerator at 1500 RPM. You can hear the turbo whistling, and then this unpleasant, rattling/squeaking sound is added, almost like a grasshopper. If I press the accelerator in fifth gear at 1300 RPM, it also rattles/squeaks, and the turbo whistling, which is normally clearly audible from around 1500 RPM, becomes noticeable as well.'

The higher the gear, and the slower(!) the acceleration when the accelerator pedal is fully pressed, the louder the squealing sound. When driving in 3rd gear up a steep hill at 1500 RPM, the car accelerates very slowly, which is normal for a 75 horsepower engine, but it makes a loud squealing noise at the front.

The squeaking must be coming from the right side of the vehicle, because it's loudest when you hear it through the passenger window and there's a wall or a row of houses on the right.

It's a little quieter when heard through the car window.

Above 3,500 UPM, it's drowned out by engine noise, but it can still be heard faintly in the background up to at least 4,000 UPM (I didn't want to rev it any higher).

I initially thought it might be the serpentine belt, as it's also located on the right-hand side in the direction of travel, but it usually makes a squealing noise that gets louder as the engine revs up. Also, it would definitely slip for a moment when starting the engine, but it's not doing that.

Does anyone have any ideas?

Is it something mechanical that's moving due to pressure differences, a pressure valve that's making a strange whistling sound, or is it releasing boost pressure because the pressure is too high?

Otherwise, the performance is as expected. It accelerates well, reaches a speed of 180-182 km/h (approximately 112-113 mph) when needed, fuel consumption is normal, and there is no oil consumption.

Thank you and best regards,

AndréV

Got my car back from the repair shop today.

The squealing sound is most likely coming from the turbocharger. It's probably a bearing failure that manifests as a squeal under load.

The new TL (presumably a part or device) has been ordered, but it is currently not available. I will receive a new appointment once it is in stock, and then it will be installed.
Thankfully, it's a warranty case, otherwise this would be expensive. Since I've driven the car very carefully for the 4000km I've had it, the engine never exceeds 2000-2500 RPM for the first 15km, and rarely goes above 3000 RPM when warm, the previous owner must have damaged it, or it's a manufacturing defect.

I think I'll switch the oil in the car from 10W40 to 5W40; it seems like a safer option.

Regards,
André.