Front End Noise

[digitallust]

Hi Guys, so I recently purchased a 2010 MY08 Polo TDi (literally last Thursday) Low KMs fully VW serviced and probably one of the most well maintained used cars I have seen. 60K on the clock. Anyhow the day I picked it up I did around 100kms putting it through its paces and everything seemed tight, fine and normal. However yesterday I did 600km round trip, problem free initially, pulling 4.8L/100 I was impressed.

This morning when I took of I noticed an unusual sound coming from the front end.
Initially I thought it sounded like a busted front end shock or suspension related. But after 20-30km of testing I am now not so sure. All different bumps and speed bump testing made it it near on impossible to replicate the noise. However the best way I found to replicate was if being in first gear I held it and not changed the gear and took my foot off the accelerator , when, as a manual, the car sways forward and backwards slightly, I can hear what I can only describe as a muffled flat sound rubber duck being squeezed. LOL my Mate who was with me during testing was puzzled also. He said it sounded like the circus was in town haha
What is more confusing is that it won't do it all the time, it may be a coincidence but from a stone cold start, it was hard to replicate it. However after driving around and it being completely warmed up made it easier to replicate the sound.

The 600km trip I did yesterday was on a relatively decent highway however there were some patches of really choppy roads and it literally rained for 500km of the 600km trip. Maybe the bumpy ride knocked something lose?

Now I am somewhat mechanically minded however this has me stumped, hoping that some of the VW Guru on here can point me in the right direction, perhaps with common issues known to my particular model? before I take it to VW.
Cheers,

[sambb]

dunno man. That in gear lift/accelerate/lift/accelerate test shows up all kinds of knocks etc but not a rubber duck being squeezed. Its not just the diverter valve (closed circuit blow off vale) venting each time you lift. If it happens when you lift yes, but not as you accelerate. Possibly an n249 canister leak. Its the black canister atop the cam cover which stores vacuum to be used as an auxillary vacuum source to pull the diverter valve open. I think the tdi's have them. You can remove the pipes of that and blow into it to see if it holds pressure. Perhaps its sucking air and loosing vacuum?? it would try to hold vacuum after each time you've lifted, not as you lift like a DV would.

[TDIfan]

Its not just the diverter valve (closed circuit blow off vale) venting each time you lift.

TDIs don't have a DV sam, not even a throttle on the engine. Just an anti shutter valve at where a throttle normally is, and it's only used to prevent the engine from shaking when turning it off.

With noise at take off/sudden hard braking, lower control arm rear bush would be my first go. It's pretty common on the 9N/9N3 models. Different degrees of deterioration on that bush gives different kinds of sound.

[simon k]

not a broken engine mount?

what if you get your mate to push it along and you step off the clutch as if you were trying to push start it (but with the ignition off)

[sambb]

Ha yeah your absolutely right. Beats me then.

[digitallust]

Thanks Guys, have to say its the first forum I have joined and found the people on here to be helpful and resourceful, not all moaning and complaining. Mercedes Benz, the worst LOL
Took your advice onboard and I am now thinking it sounds more like control arm bushes or suspension related.
Was out testing it today for about an hour in total. The interesting thing is in the mornings, it is quiet, not a noise anywhere, once its warmed up and been driving for a while all the squeaks come all at once.
Ive was rocking the car, in second gear, driving, accelerating then taking my foot off and on again and it squeaks back and forth. Even coming to a stop at traffic lights after rocking it back and forth, tapping the brakes replicates the squeak. It now also squeaks over sharp bumps in the road, but again only once the car is hot and been driving around for a while.. thats the bit that has me stumped.
My mate says he doubts engine mounts as it would be thumping under hard revs etc.
Guessing a trip to VW is in order. Ill be happy if its suspension related.

[simon k]

given you can replicate it at will, you could grab a can of WD40 and spray a few things.... test, spray, test.... or get VW to sort it out

please let us know what it was when it's fixed!

[TDIfan]

If you get the standard LCA bush, you might need to do it again in a few years time. It's designed to fail in my own opinion. I has two massive voids in it, basically it looks like an I inside an O and the rest is void. I would fill the voids with poly base adhesive, or simply get a seat cupra uprated bush. It is a solid rubber bush without any void, it'll probably last till the end of the car's life.

[sambb]

yeah check those rear lower control arm bushes. Look closely with a torch and look for splits in the narrow parts of the bush. Also with the car just sitting in the driveway turned off, if you grab hold of the plenum and push and pull the engine back and forth towards the firewall will that make the noise happen? If so it could be the dogbone bush. try that.

[sambb]

also spray some spray on lithium grease or something like that into the frobt anti roll bar bushes and then get your weight rovking up and down through the fenders to work it in. It could be that as the nose dives/lifts as you get on/off the accelerator that the front anti roll bar is squeaking within dried up rubber original bushes. If it goes away for a bit after the spray, that could be it.