A5 3.0 tdi quattro 2008 CAPA. Loud whistle

[Don Etchells]

Morning everyone, just repaired my partners car and now have a very loud whistle on boost.
History: found that the car was spraying a fine oil mist from the air intake manifold as someone had previously used gasket glue to seal the upper to lower manifold. After hours and hours of unhelpful info from Audi I eventually worked out that the lower manifolds had been replaced but someone had purchased the wrong type which have a mating face with no gasket seal. The upper manifold is of the cast type, so also has no gasket seal.
The ones fitted are not for the engine code CAPA and should have a suffix of BT and DC
So long story short, I removed the upper air intake manifold and made some gaskets to replace the glue someone had previously used.
Bearing in mind no previous issues to the car or no ECU faults stored.
So on replacement of the manifold we now have a audible sound in addition to any normal turbo boost whistle.
Can anyone advise please?
Seen a previous thread indicating a hose inside the front wing?

Catch tank required for excess oil in air intake is another issue I think.

 

[Jordan Coulson]

Sounds to me like a air leak? Possible split hose or maybe you have forgot to tighten a clamp etc

 

[pelhamsdetailing]

Undoubtedly. If you've checked everything is tight and on correctly and are hearing a hiss, then it could now be from another point.

You haven't said where it sounds like it could be coming from, but it would seem likely its from where you have performed your repair work.

I thought the upper plastic manifolds had rubber seals on top and bottom fitted where they connect to the lower intake and the top cast intake from the intercooler? Perhaps there is a gap in your application of said glue?

 

[Don Etchells]

Hi Vappy, Thanks for your reply, Yes I can confirm that all torques are as per the manual. The sound comes from the turbo area and is more of a screech than a whistle. Baring in mind there are no previous issues or faults with this car. All I have done is replaced a bodged gasket(glue) with a correctly made one.
Yes you are correct the lower manifold should have the green type gasket seal groove in the so the cast upper manifold will seal. unfortunately someone has purchased the wrong lower manifold and glued it to the cast upper. This mastic seal failed. after replacing it, it appears that maybe I may have sent the pressure somewhere else?

 

[Don Etchells]

Sounds to me like a air leak? Possible split hose or maybe you have forgot to tighten a clamp etc

Thanks for the reply Jordan, Yes I am beginning to think it is possible I may have fixed one problem but pushed the pressure elsewhere.

 

[pelhamsdetailing]

Hi Vappy, Thanks for your reply, Yes I can confirm that all torques are as per the manual. The sound comes from the turbo area and is more of a screech than a whistle. Baring in mind there are no previous issues or faults with this car. All I have done is replaced a bodged gasket(glue) with a correctly made one.
Yes you are correct the lower manifold should have the green type gasket seal groove in the so the cast upper manifold will seal. unfortunately someone has purchased the wrong lower manifold and glued it to the cast upper. This mastic seal failed. after replacing it, it appears that maybe I may have sent the pressure somewhere else?

Right, gotcha. I can see that more clearly in my mind now. I had a very similar sounding issue now that you mention this screeching sound coming from the turbo. Check your bolts on the DPF to your turbo. Under any form of boost I had a loud screaching noise, which turned out to be due to missing one of the bolts that fastens the DPF to the turbo, and air was escaping that way. The gasket was also blue, but the gap was half a millimeter. I've replaced the bolts and all is well now, so if you haven't already, that might be a good port of call.

edit: The gasket, 3 studs and 3 nuts to replace the ones holding your DPF to the turbo are about £12 from audi and are a readily available item in stock according to my local audi at the time.