Help Please - what is this sound

[V6_Man]

Hi folks,

I have a B7 Sline, 140 Tdi multitronic, 68k miles on the clock and with a BRE engine (not sure whether to smile or cry). I started getting this strange sound back in August and ran a scan twice. Both times no faults found with the most recent scan being yesterday.





I am not sure what this sound is (not experienced enough to identify or relate it to a specific part). Below are the "symptoms":

1- It only happens when the engine is warm and running for sometime.
2- It doesn't happen every time you start the car even if the engine is warm.
3- Sometimes it would crank but start (like in the video)
4- Other times, it won't start making the same noice (as in the video).
5- Sometimes when it starts it leaves smoke (believe it is black)
6- You turn off the ignition and re-start and no noise, at all. It would appear the problem doesn't even exist.
6- There is no engine sound at all whether the car is idle or running. This happens only while starting the car.
7- It doesn't happen when the engine is cold or you start first thing in the morning.
8- It is not weather dependent as it is happening these days. Not that it is snowing outside but ...

I tried 8-10 times just to record the attached video and it happened only 3 times. Rest was absolutely fine. I know sometimes it is really difficult to identify the root cause from the video but any help/pointers would be highly appreciated.

 

[joinerman]

Sounds like the starter ring gear to me

 

[V6_Man]

Sounds like the starter ring gear to me

Thanks for your reply @joinerman. I am not technical enough so apologies for asking a dumb question. If it is the starter ring gear would it not have effected the DMF? Can you replace the ring gear on its own or is it full kit you have to replace? Or is it that we have to take out the DMF check the condition, e.g. bad teeth and if so, change the DMF. It is a multitronic gearbox.

 

[carlcall]

At first I thought DMF....but as it's only a 140 could it be CAT flexipipe to exhaust? I only ask as I know that the 170 has a bracket that fixes it to the side of the gearbox.

 

[V6_Man]

Thanks @carlcall. So, a loose / damaged flexipipe could potentially cause this noise and therefore stop engine from starting?

 

[carlcall]

I couldn't see it stopping the engine from starting.

Does the engine turn over when it doesn't start?


Sent from my iPhone using Tapatalk

 

[V6_Man]

It does indeed.

 

[carlcall]

Have you taken the top cover off the engine and checked to see if anything is loose or get someone to keep starting it to see if you can find the area the sound is coming from.

It could be the ring gear but it could also be the starter motor.

But if the engine turns over and doesn't start it's go to be something that's loose that's causing both the noise and not starting.


Sent from my iPhone using Tapatalk

 

[V6_Man]

Have you taken the top cover off the engine and checked to see if anything is loose or get someone to keep starting it to see if you can find the area the sound is coming from.

It could be the ring gear but it could also be the starter motor.

But if the engine turns over and doesn't start it's go to be something that's loose that's causing both the noise and not starting.

Sent from my iPhone using Tapatalk

Did it the other day when I scanned the car from both above and opened up the under tray but couldn't see anything visible at all. I going to have to ask my Indy to look in to it further as my limited knowledge / skills stop here, plus I don't have enough tools either.

 

[V6_Man]

Let's hope it is not something big as I am replacing discs and pads (MTEC drilled and grooved discs and Mintex pads), and upper control arm on both sides as o/s bush seems worn out a little bit.