Hissing Noise 170 Tdi

[N417H4N]

Seem to have developed a hissing Noise from the engine, this cannot be heard until you open the bonnet and is not there while the engine is running.

Sounds as if it's coming from the little black hose on the right hand side.

Any ideas if this is normal or not?

 

[Rideen]

Sounds like some kind of a boost leak, but I might be wrong.

 

[N417H4N]

Sounds like some kind of a boost leak, but I might be wrong.

Doubt it's a boost leak as can only hear when shutting engine off, plus It pulls really strong and no fault codes for boost.

In fact there's no fault codes at all for engine.