Mystery noise (and hearing test)

My 2003 currently has 306K miles. I want to chip it and add big injectors, but I'm trying to work out all the niggling issues to make sure it's sound before I add power.

I've resolved 2 of 3 such issues. The one left is a high-frequency noise generated when engine braking at about 3000 RPM or greater. I recorded this noise so you can help me identify it. To do so, I descended an 8% grade in 3rd gear at about 45-50 MPH, which puts the engine at about 3000 RPM. The noise goes away if I gently blip the accelerator, and comes back when I take my foot off. You can hear the noise coming and going as I do this. I made the recording with the windows down, an there was terrain & a guard rail reflecting the sound back at me, which made it easier to hear.

The first video has no audio filtering. You can hear the noise, but only just barely and if you know what to listen for. In real life, it's easier to hear it. In the second video, I used Audacity to apply a hi-pass filter to make the noise stand out.

If you have high-frequency hearing loss, you may not be able to hear the noise at all.

My WAG is valve float, the noise being valve stem striking the lifters when they end the float? But this is an uneducated guess.

No audio filter--
https://youtu.be/EUc8-Uz_Jxg

High-pass audio filter--
https://youtu.be/teg2NqwJvxM

Just to review, after our telephone convo...

Rear brakes glazed, stuck calipers, collapsed e-brake cables, Wheel bearings, EGR manifold to EGR pipe.

Since it happens only when moving, the chances that is a 'valve issue' is at best, remote. And the LAST thing TDI engines do is valve float. The rpm's and the running height of the valves is absolutely not prone to anything remotely like the noise you are getting.

I think I would try rolling like you were with 'engine off' to see if the problem can be appointed to engine or suspension.

One other issue in the 03 engines are the boost pipes, which I see you have the VNT-17, which we give warnings about the amount of CRAP turbos we have seen. We will not install a Chinese turbo. Unless the place of manufacture for Garrett is other than China, we refuse them. Also, there are two known seal leak areas for the boost piping for the adaptation for the VNT-17. Usually, the Gates boost pipe, with snap-in connections between the turbo and pancake pipe works great. However, there are two viton seals which we have seen pinched or loose that could cause a running noise. Boost leaks can be very vexing, as they often only cause noise under an exact condition.

Let me know what you figure out. If you have injectors cleaned, be sure to check the idle balance and then, we do another tricky check that will show second stage results. NOP2 is where the injectors provide the largest amount of fuel with the greatest possibility of variation.

Good luck.

Frank

Frank, thank you so very much for your response and the half-hour you spent talking with me by phone yesterday. I really appreciate your input and the time you took to respond.

You have lots of good ideas. I think you've convinced me the noise is not valve float. I have a GoPro camera that I have in the past mounted under the car to help diagnose other issues, so I may see if I can do that again to pinpoint the exact source of the noise. I'll post results to this thread as I gather new data. Right now, I think my top suspect is the turbo.

I don't know where my VNT17 was made; I got it from AA Rodriguez, along with his aluminum adapter for the compressor output to the stock clip-style hose. That connection has worked, but it's not hard to get the hose to unclip, and a couple of times I've had to reposition things to get it back together. I will look again at this more closely. I've been running this setup for about 110K miles / 4 years. In general, I agree about Chinese CRAP - Chinese Replacement Auto Parts.