Weird Metallic sound when accelerating?

[Cupracabra]

I have a Cupra ST 290 2016. Really satisfied with the car except for some squeaking when going over bumps and a weird Metallic sound when accelerating.

The sound is a bit hard to explain, but I first thought it was coming from the brakes, but I have noticed that it changes frequency with the rpm. I can only hear it at 1-3k rpm. It sounds a bit like metall on metall or a slight rattle. I can't really hear anything when opening the hood. Is it perhaps the DSG?

i have recorded a video of it, but it's really hard to hear it.

9 april 2023

youtube.com

Loose screw or vibrating plate near the turbo? That wouldn't really explain the change in frequency with rpms.


Any ideas?

 

[oldglosracer]

Catalyst rattling?

 

[Slickric21]

Think it’s normal at a certain rpm whilst accelerating.
Seen it lots of times on various car groups on this platform

 

[Cupracabra]

Catalyst rattling?

Think it’s normal at a certain rpm whilst accelerating.
Seen it lots of times on various car groups on this platform

Could be the cat.

I have also seen this discussed on the forums, but I have never actually heard the sound people talk about.

 

[Mr Pig]

So, long story. May not be exactly what your issue is but a useful comparison.

When we bought my wife's car, a 2017 FRTDI, there was a slight metallic rattle at certain revs on the test drive. Back at the showroom I told the owner about this and said I wanted it checked out. He work shopped it and said it was the timing belt so they would replace it. I knew it wasn't the timing belt, the pattern didn't fit, but the car was two years old so hey, free timing belt.

Bought the car, it got the new belt, noise still there.

So it went back in and this time the techy-bod said it was the turbo. Ok, that might fit.

Turbo replaced, noise still there!

By now the dealer is getting a bit less cooperative. They've replaced the turbo and the timing belt and don't seem very keen to keep replacing things. The owner says that they don't think it's serious but if anything does go wrong while we own the car they'll cover it. Wasn't all that happy with this but they weren't going to do anything else.

I took the car to tuning specialist who seems to know his stuff. Him and his tech spent a bit of time under the bonnet and said it was something in the intake area but they'd have to strip it out to find it. I wasn't confident enough that they knew what it was so I left it.

Maybe six months or so later the noise got a little worse. It was happening at more places in the rev range so I figured it might be easier to find. I got my wife to hold the car at certain revs while I prodded around. Eventually I moved the pipes going through to the heater and it stopped! That's all it was. A little bit of chatter, I think it was the heat shield but I'm honestly not sure. Noise stopped and has never returned.

Morel of the story? It could be a lot of things, it might not be serious and don't think that because someone works in Seat garage they'll have a damn clue what it is.

 

[Cupracabra]

So, long story. May not be exactly what your issue is but a useful comparison.

When we bought my wife's car, a 2017 FRTDI, there was a slight metallic rattle at certain revs on the test drive. Back at the showroom I told the owner about this and said I wanted it checked out. He work shopped it and said it was the timing belt so they would replace it. I knew it wasn't the timing belt, the pattern didn't fit, but the car was two years old so hey, free timing belt.

Bought the car, it got the new belt, noise still there.

So it went back in and this time the techy-bod said it was the turbo. Ok, that might fit.

Turbo replaced, noise still there!

By now the dealer is getting a bit less cooperative. They've replaced the turbo and the timing belt and don't seem very keen to keep replacing things. The owner says that they don't think it's serious but if anything does go wrong while we own the car they'll cover it. Wasn't all that happy with this but they weren't going to do anything else.

I took the car to tuning specialist who seems to know his stuff. Him and his tech spent a bit of time under the bonnet and said it was something in the intake area but they'd have to strip it out to find it. I wasn't confident enough that they knew what it was so I left it.

Maybe six months or so later the noise got a little worse. It was happening at more places in the rev range so I figured it might be easier to find. I got my wife to hold the car at certain revs while I prodded around. Eventually I moved the pipes going through to the heater and it stopped! That's all it was. A little bit of chatter, I think it was the heat shield but I'm honestly not sure. Noise stopped and has never returned.

Morel of the story? It could be a lot of things, it might not be serious and don't think that because someone works in Seat garage they'll have a damn clue what it is.

That's interesting, could you send me a photo of the piping you movement. I guess you just moved them a few millimeters?

Think it’s normal at a certain rpm whilst accelerating.
Seen it lots of times on various car groups on this platform

As Slickric21 said a lot of people talk about this on the forums. Some have suggested that it's because of a cat rattle and when you replace the downpipe it goes away. The TDI is a different engine ofcourse, but the piping layout could be the same.

 

[Mr Pig]

That's interesting, could you send me a photo of the piping you movement. I guess you just moved them a few millimeters?

Sure. It's right behind the engine. I think it's two alloy pipes going into the bulkhead. I couldn't even tell you what exactly I moved. I was just pulling and pushing things around trying to find the noise when it disappeared. I think it was the metal flanges next to the pipes but I'm not 100%. I'll get pictures later.

 

[Mr Pig]

Where the alloy pipes go into the firewall, possibly the plastic ones too? I can't remember but it was in that area, I just moved something slightly and the noise stopped.

 

[Cupracabra]

View attachment 36491

Where the alloy pipes go into the firewall, possibly the plastic ones too? I can't remember but it was in that area, I just moved something slightly and the noise stopped.

Thanks!
Will try it. How did you move them, you just pushed them randomly?

 

[Mr Pig]

How did you move them, you just pushed them randomly?

Yes, pretty much. My wife was in the car listening to the noise, you couldn't hear it from under the bonnet. I was just holding things, shoving things around. I think it was something behind that silver foil heat-shield?

There are lots of little bits and bobs connected to the bulkhead and even a slight vibration can be amplified. You need to try and be logical and think about what sort of sound it is, where it might be coming from etc. What does the pattern match up with. I'm sure that most of these lightweight noises are nothing to worry about but you want to know don't you?