Common boost leak areas? (2006 S3 8P)


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Mar 12, 2007
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I've recently noticed that if i put my foot down and get a surge of boost, there is a noise that is almost like a whistle/whoosh noise.
Very hard to explain, but very easy to initiate as it happens when boost kicks in no matter what gear.
The car still drives very well, so it's not a complete loss (like my old split DV was).
It has a new DV fitted and recent inspection does not indicate any issues, so I'm thinking it could be a hose or clamp?
If anyone has experienced this or knows a good place to start looking, I would appreciate any tips.
I think it’s six 2 between turbo and inter cooler, then two to the inlet pipe and two for the throttle body connector, you get what you pay for these are strong clips not like the cheapo stock rubbish. Should be 40 to 60 quid

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I remember replacing a seal on one of the intercoolee pipes down by the crankshaft pulley as there was oil coming out of it and onto the engine tray
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Thanks for the links for the clamps. Whilst I don't want to spend a fortune on them, I do understand that good quality comes at a price.
To me, that price has to be justified.
Firstly I'd prefer to identify IF there is a leak (or not, could be a sound I'm not used to hearing but is normal on this engine) and where it is.
If the hose or seal are common failures, spending £60 on clamps is a huge waste to not solve the problem.

I'll take a look around the crankshaft pulley area and see if there are any signs of oil to indicate a seal leak, thanks @-Ju- for the suggestion.
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I've had a quick visual look around the intercooler hoses, but haven't got the means to get the front end raised at the moment.
I can't see any signs of oil or loose connections, but I will attempt to check it more thoroughly soon.
Common areas are PCV, intercooler pipes (where they connect to IC), intercooler itself (if you have plastic end caps), DV
Common areas are PCV, intercooler pipes (where they connect to IC), intercooler itself (if you have plastic end caps), DV
Cheers for the info.
IC does have plastic end caps, so will get them checked.
DV is 2 months old, max. Revision D so should be good. I did double check it was fitted correctly and it is.
Is there an easy way to test the PCV? It idles ok so I think that rules it out?
IC pipes need closer inspection when I can jack the front up.
Is there anywhere local that can do a smoke test for you? That will highlight any problems straight away.
I'm close to a regular garage, but don't know if smoke testing is more specialist or if all garages do it?
I'll drop in there at some point and ask.
Doesn't need to be smoke tested, most specialists insert a bung with a valve on the intake to the turbo and pressurise the system and listen for leaks.

Odd that you've got a plastic end cap IC as they were only fitted to the facelift S3. If you're mapped I would swap this out as it felt like I'd had a mini remap when I did mine!

PCV was updated with a new revision so may as well fit that - circa £40. Also dipstick has been known to fail£11 for updated one, but as you say, usually means idle issues.
My Dipstick is orange, so I presume that is the revised version?
No idle issues so I don't suspect the PCV, but it is on the list of things to change eventually as I know they do fail.
I'm fairly sure the IC had plastic end caps, looking from the top down on the passengers side it certainly looked that way, but I'll double check.

Have double checked and I was wrong, it is metal but very dirty.
I put my phone inside the engine bay from below and got a photo which luckily captured the part number 1K0 145 803P which identifies it as the correct part.
So we can rule that out.
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Yes, but the hose connections at the bottom are still prone to leaking boost - you should be able to see as it leaves oil deposits near the push-fit connections.
Looks pretty clean on this side, can't see the other side with getting the car raised.


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We had a look under the car today, and all hoses and connections looked to be fine and there were no signs of oil escaping.
We had another go at patching up the broken base of the airbox but that made no difference.
Having thought about it quite a bit, I decided to re-fit a cheap replica DV I bought a few months ago (thinking it was genuine). This has fixed the woosh noise whilst the car is on boost, so either the DV is meant to do this, or the Pierburg DV isn't up to the job (but the fake one is?)

I'll leave the fake one fitted for now and monitor it over a few miles and see if it feels different or sounds better/worse.
If it seems to perform better I'll run a few logs and go from there. May end up getting a GFB DV+ at a later date.
I've been away for a few days on a course, and on the journey there and back I have been able to confirm that the leak is still present, so that rules out the DV.
If the hoses are good and the DV is good, what else could it be?
I've ordered a new N75 valve as the symptoms from a failing one sound similar to my problem.
Also emailed a few local garages to see if they can do a leak test, but have a DIY option available if needed.
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What’s the diy version

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I was quoted £60 for a smoke test by one garage, and one never responded.
The DIY method is to use an air compressor and seal off the inlet just after the MAF, pressurising the system and listening for leaks and using soap water to detect bubbles (like fixing a bike puncture).
I know someone with the air compressor so we will give it a go and save £60.
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I’m keen to see the outcome of the N75 replacement.

On YouTube, there are a couple of videos of DIY smoke tests if the soapy water doesn’t yield any result.
If i mind right the Yellow dipstick is the newer one as i had to get 1 recently as the rubber o'ring had pershied
I'll look into the dipstick situation, thanks.

I reverted the car back to stock map today and did a few hundred miles. The air leak isn't audible, but on occasion I can feel it, so I think it could be the spring in the DV being a bit weak.
I have ordered a DV+ and will fit that at the same time as the N75 in a few days time. We will try the DIY pressure test first to double check where the issue may be.
Hi Davey did that solve your problem?
Hi Davey did that solve your problem?
Sorry for the late reply, I've just started night shifts this week.
I have cured it, but that was from finding and replacing a cracked PCV hose at the top of the engine. The hairline crack was impossible to see and the only clue that there was a fault was a slight misting of oil on the underside and front edge of the engine cover.
Initially I suspected the DV+ was at fault, but when I ruled that out I removed the plastic hose and inspected it carefully and spotted the crack.
Replacing that cured my oil loss and restored some power, so it was a cheap and easy fix.

Hope that helps.
Great can you send the part number or pic of the aforementioned hose? This will help others when google searching too
I don't have the part number to hand, and it's too wet to be going to the car and removing the engine cover to take a photo of it.
All parts can be easily identified using this:
It's how I located the part number in the first place and then the part can be sourced cheaply online or by visiting a dealer/TPS.

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