Metallic rattle like noise when throttle input reaches max speed?

[AudiA3B]

Hi. There is a metallic rattling noise from my A3 S-line 1.4 COD 2016 facelift.

It happens when the amount of throttle I give can't make the car go any faster?

Example: I am in 2nd (or 3rd, 4th or even 5th) gear giving just enough throttle to keep it at 20mph or whatever speed relative to what gear I am in? And this metalic rattle noise starts from the engine area.

The noise will go away if I remove the throttle or speed up.

I can't reproduce this noise when the car is stationary by revving it or holding the revs, it only happens while trying to maintain a speed?

It only happens when the car won't go any faster than what the throttle I am giving will allow it.

If you think of using cruise control to maintain 30mph, this noise starts when the car reaches and tries to maintain 30mph. I can only hear it with the windows down.

Help and any pointers please.

 

[Mikeso51]

Some early 1.4 engines were plagued with a rattle exactly as you describe which came from the turbo wastegate actuator rod resonating under certain operating conditions. Audi claimed it wasn’t a problem operationally, but after many complaints came up with a “fix“ which from memory was a simple clip to reduce the free play In the linkage. This problem was supposed to have been designed out on the newer 150bhp engined cars, but there have been instances of it still occurring, and when it does the simple fix used previously doesn’t work. If you search the archives there was a chap a couple of years back with a 1.4tfsi Sline of the same vintage as yours who had this problem. Thankfully his car was under warranty at the time, because Audi said the linkage wasn’t adjustable or replaceable separately, so their solution was to replace the complete turbo assembly! I don’t have this problem on my car, so I have never needed to explore it further. However, if this problem is indeed the source of your rattle I can’t help but think that there must be a simple solution to reduce the free play and/or dampen the resonance.

 

[AudiA3B]

Is there anyway to test that this is where the noise is coming from? I searched eurocarparts for a new turbo and it was not cheap I cant make the noise when the car is stationary so harder to see where its coming from.

 

[Mikeso51]

You need to be very sure that this is the source of your rattle before spending £££ on parts. If you search on the web there are various relevant threads, mainly relating to early 1.4 engines, and some sound clips you could compare to your car. The wastegate actuator rod is easily accessible at the back of the engine, so you could try jiggling it (technical term) to see if there is a lot of play in the linkage, and if the noise sounds familiar. Be careful if the engine has been running because this area get very hot! I seem to remember that there was a test that Audi came up with which involved clamping a small weight to the rod to change its resonant frequency. If you search the archives/web you should be able to find more information.

 

[AudiA3B]

I jiggled it a bit and there is quite a bit of play and noise in it...

Here is a video..



Thoughts? I guess I will need to get a video camera or an old phone attached somehow and recreate the noise while driving to see if that's what the noise is..

Hopefully I can buy just that rod? or a clip? A whole new turbo seems to be crazy money

 

[Jcbmally]

I jiggled it a bit and there is quite a bit of play and noise in it...

Here is a video..



Thoughts? I guess I will need to get a video camera or an old phone attached somehow and recreate the noise while driving to see if that's what the noise is..

Hopefully I can buy just that rod? or a clip? A whole new turbo seems to be crazy money

Yup, source of rattle.

 

[AudiA3B]

Thanks, can I buy just that rod? Any suggestions on where to go? I imagine Audi will not sell that rod separately.

Not sure how to find out what model of turbo I have to try and find out prices etc.

Might see what my local independent Audi specialist says but since they were wanting to charge me £260+vat to fit a front wheel bearing unit , it kinda put me off that garage.

 

[Jcbmally]

Thanks, can I buy just that rod? Any suggestions on where to go? I imagine Audi will not sell that rod separately.

Not sure how to find out what model of turbo I have to try and find out prices etc.

Might see what my local independent Audi specialist says but since they were wanting to charge me £260+vat to fit a front wheel bearing unit , it kinda put me off that garage.

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