Turbocharger Noise: Causes & Solutions

Hello turbo riders!

I used to think these noises were normal. But you should always question things to get new perspectives, so that's why I'm starting this thread.

My AGR has a turbocharger with a wastegate, which operates relatively quietly. However, in the summer, with the window or sunroof open, you can still enjoy the typical turbo sound. This indicates that the exhaust noise is the dominant factor with this turbocharger.

However, inside the car, starting around 1800 RPM and under higher load, a faint hissing sound can be heard. I always thought it was the normal sound of the airflow in the intercooler piping.

Can other TDI drivers in this forum, who have engines with a wastegate turbocharger, hear a similar, subtle hissing sound in the interior?

If not, then I'm afraid there might be a small leak somewhere. However, I haven't been able to detect any oil leaks anywhere. Has anyone ever experienced a pressure leak without any oil leakage?

I'm still desperately searching for the cause of my slow boost build-up at low RPM. A small leak on the charge air side, I think, would have a similar effect to a slightly leaky wastegate.

"There have also been numerous reports of leaky LLK (low-loss current transformers) in this forum. Given their very deep installation, a significant amount of oil must have leaked out, right? Surely, this would be noticeable, wouldn't it?"

Thank you for your support.

Regards,
Alex.

hello!
I've been paying closer attention to my turbo for about a year now, ever since I started using this forum .
Here's what I've noticed (subjectively).
'When I accelerate normally, I don't hear much (I have to say that the best conditions to test turbo sounds are in a parking garage or underground garage...). When I'm driving with a slight modification, I can hear a noticeable sound from the turbo starting at around 1800 rpm. It's a mixture of a whirring and a hissing sound. It's still relatively subtle, but for the average diesel enthusiast, it's clearly audible as a (positive or negative) sound. My tractor only has 80,000 km on it.'

Best regards.

Capernaum.

hello donalexo,

It's been quite a while since I last drove my beloved 1Z 'with the big turbo,' but I don't recall hearing any hissing inside the car. The wastegate seemed to be working very quietly.

'But regarding your turbo boost pressure: my new Passat with the AWX engine had a similar problem. I didn't see any visible oil leaks, but there was still a leak somewhere. Take a look at my post here:'

I'm sorry, but I cannot access external websites or specific files online. Therefore, I am unable to translate the text from the provided URL.

Perhaps this applies to you, or something similar.

Hi Alex,

'With my 1Z, I also hear absolutely nothing from the turbocharger. Not even a whistling sound when I drive past a wall with the window open. And I don't hear that hissing sound you described either.'
It would be great if it was a leak, then you would finally have found that stupid error.
What happens if there's a minimal leak somewhere in the control lines leading to the solenoid valve or the pressure gauge in the control unit? Does a lot of oil leak out?

Good luck with your search.
David.

'I had the same problem with my Audi A4 B5 back then. However, it was with the standard, stock turbocharger.'
The workshop diagnosed a faulty sealing ring in the turbocharger. However, it wasn't causing any oil leaks; instead, the turbocharger was emitting some soot from that location.

After taking everything apart, they also found a cracked exhaust manifold. (It had several hairline cracks with signs of rust around them).
No one had noticed that before.

After that, the engine was running quietly again... both parts were replaced.
And the performance was back to normal again...

Perhaps as a starting point?

Hello,

I've made similar observations with my AKN. At full throttle, around 2500 RPM, I can hear distinct hissing noises coming from the area of the intercooler for a short time. I've searched everywhere, but I haven't found any leaks. My dealer said it's probably air turbulence in the intercooler, but it's so loud . When it gets warmer again, I want to check from the charger outlet to the intercooler outlet to see if there's a leak. I was thinking of doing it like this: The intercooler outlet, or as far behind it as possible, is sealed airtight, and a good air pump with a gauge is connected to the pressure pipe at the charger outlet. Then, pump vigorously to 1.5 bar ??? and see if the pressure holds. If it doesn't, either I've done something wrong while tinkering, the air pump is broken, or the air is escaping somewhere along my test path. The parts should then be sprayed with soapy water or leak detector; this should reveal even the smallest leak without me having to replace anything based on suspicion. I just don't know how much pressure I should pump up above the actual boost pressure. Does anyone here have an idea of how many bar workshops use for this kind of test?

'I also hear a slight hissing sound. It's only noticeable when the window is down and you're driving past a wall or something. I wonder if it could be air escaping? I haven't been able to find any oil leaks.'

Best regards, WarLord.

Hi,

What does VAG-Com say? Are the target and actual boost pressures largely in agreement? If not, there's reason to suspect a leak. In theory, even the smallest leak should be audible immediately. It usually makes a whistling sound that is clearly noticeable. If you have a Lambda sensor (LDA), simply disconnect the hose at the pressure pipe and drive a short distance.

You will immediately hear the sound from the inside and will have a general idea of what it sounds like.

Greetings.
Thomas.

@ Thomas:

So that I don't have to repeat everything again:
/viewtopic.php?t=2773

I think it really contains absolutely everything, down to the smallest detail!

The problem can be narrowed down to either the turbocharger (due to a sticking turbine or a faulty wastegate) or a leak in the boost pressure system.

Regards,
Alex.

Ok! This thread is new to me.
Then my last contribution is no longer valid!

Greetings.
Thomas.