Strange sound (hiss/metal noise) Turbo? Boost leak?

[jmejamie]

Hi guys!

I have an Audi A6 2002 AWX 1.9 TDI PD130 and i have a concern!

Basically when i accelerate i get this hiss or metal kind of sound from the engine but i hear it in the driver seat whilst driving. Its loud in person but my recording you can hardly hear it. Its only when accelerating or cruising at set speeds (maybe bang on the turbo spool).

As soon as it starts the noise is in the background then my phone vibrates and just after that i start accelerating and you can hear the sound again: carsoundMP3 - Jumpshare

Wondering if anyone else has this sound? (my friends car exactly the same year and engine doesn't)

I have a feeling its boost related because its as it really spools up.

I have a Darkside Developments EGR delete kit fitted
I have also secured main top pipes from intercooler round the back of the engine into the delete kit with PTFE tape and cable ties so they are sound.

Any help would be awesome guys!

Not sure if its related but the car also smells a fair bit after driving and sitting idle at lights, enough that with the windows down the car stinks inside. I had the cat/exhaust checked but its fine...

[Rob69]

Follow the exhaust out of the turbo and down towards the cat, you'll see an expansion piece, looks like it's wrapped in wire mesh, check that for leakage, it may not have been picked up during your initial exhaust check. Failing that check the boost air pipes and intercooler, but the fact you're getting fumes in the car would make me suspect the flexi joint.

[jmejamie]

Hi Rob

They checked the Flexi joint and apparently there isn't anything coming out of it. It's funny because when the internal fans are on you smell it more in the engine bay. It's almost like there's a leak near the front of the engine. To be clear there's no smell with the windows up inside the car.

When you say boost air pipes what do you mean?

[Rob69]

By boost air pipes I mean the turbo compressor outlet pipes, down to the intercooler then back up to EGR valve and engine intake manifold. If the exhaust flexi is ok I'd check the exhaust manifold to EGR pipe, I don't know the details of your EGR delete, maybe this pipe has been removed already ? If not removed, this has a short bellows section that may be cracked, or the bolts might be loose.

[jmejamie]

Hi Rob

Checked the boost pipes today, managed the drive the drivers side wheel up onto some stacked wood so i could get under it! I took the pipe off the bottom of the turbo for the sake of it and put some PTFE tape under the rubber seal so it should be more snug incase it was that. I also took the pipe off the bottom of the intercooler where it meets the pipe that runs from the drivers side to the intercooler. Some oil was sitting in the bend there so let that drain out, cleaned it all and secured again. As for the EGR side of things i am using a Darkside developments delete kit so there sno EGR or EGR pipe, its got a plate on top of the turbo and then the pipe in place of the EGR.

Not sure what effect will have yet as i've added some high temp silicone around the tandem pipe joint that notoriously gets loose on these. Just added the silicone to stop any leaking vacuum (if any) and also give it a bit more rigidity!

Hopefully will get to the bottom of this. Is there anything else that might be causing such a loud turbo whistle/metal/hiss sound from my sound clip?

Thanks!

[Rob69]

Worst case is the turbo itself is knackered and making the noise, ( I can't listen to the sound file on work PC!) you could check the turbo shaft end float and radial play by removing the intake pipe and moving the shaft with your fingertips, you should be able to feel only a tiny bit of play. Did you check the intercooler end headers and the seams around them for leakage. I'd be wary of trying to pack out the boost pipe o rings with ptfe tape, if it starts breaking away and getting blown through could cause trouble, if the o rings looked worn get new ones.

[jmejamie]

I think I checked the turbo a while back and it felt pretty good...

Have driven it a bit today and it doesn't make as much noise now after I tightened a few bits up! Also feels like as I change gear the car doesn't lurch back! Feels like it's holding some boost as I slip into the next gear if that makes sense? Also noticed the grub screw on my delete kit was seeping some oil so I cleaned it out and slapped some high temp silicone in the hole to cure it.

When I mentioned the PTFE tape what I did was removed the rubber ring and fitted the PTFE tape tight into the slot and then put the rubber ring back into the groove to make it stick out a little extra.

Will drive for next few days and see how it is.

[03Allroad]

If it helps I had a 1.9 PD 130 Passat that one day started making a whooshing sound when accelerating, traced it to a split in one of the rigid intake pipes that you couldn't see. got a replacement from GSF for about £25. power didnt seem to drop but I guess that because it was just sucking in more clean air and bypassing air filter..

[jmejamie]

Hi 03Allroad

Thanks for replying, i check this however i couldn't find anything split on mine. I did however find that the flexi pipe had broken in such a way that i couldn't see! It hadn't split the criss cross metal on the top but the inside ribbed part had split on the catalytic converter side of the flexi which had allowed the exhaust to drop slightly enough that exhaust gas coming from the turbo was partially going out its usual pipe however where is had dropped ever to slightly it meant it was whistling out of the gap! Had it replaced now and it seems alot less whooshy! However it is still very metal sounding its hard to explain! I removed the intake pipe and tried to move it with my fingers but it hardly feels like its moving so that must be a good sign?!

Still have a strange smell though that smells like exhaust gas but isn't coming from the turbo back (unless you stand next to the backbox obviously)

[03Allroad]

glad to hear you got somewhere even if problem not fully fixed. I have to say I always had fumes coming from the front of my passat that I couldn't trace and always worse inside the cabin when raining??? - in fact it was the biggest reason for wanting to change (although still with me on my drive at the moment!) I actually wonder if the EGR had been removed as Ive never had a diesel car smell as bad as this one....

sorry not much help I'm afraid!