P0234 overboost and police siren noise

[altea-ego]

I had a police siren noise between 1400-1800rpm after only 33K miles, under light acceleration/deceleration. When flooring it, it went into limp mode and was then fine after a restart. No check engine light was on, but an error code P0234 turbo overboost was logged. Local VAG specialist said turbo out of balance and rebuild/replacement required. I had previously tested the variable vane operation on the turbo using a hand vacuum pump and it seemed to be moving the full travel.

After removal of the turbo for replacement I found that the variable vane lever would only move freely half of the travel. The turbo was indeed clogged with diesel soot. Hope this helps someone as I ended up with new turbo when just a clean/rebuild was required. Make sure you disconnect the vacuum cylinder connection when testing.

Youtube video showing problem here.

http://youtu.be/rsyuOFXKCeE

 

[tomlegg]

Does anyone know if this can be rectified without removing the turbo? My toledo seems to do the same thing but has no power loss etc!! Doesn't go in to limp mode but makes the siren noise.

 

[Viking]

My Altea made the siren noise right up til 140k miles when I sold it. Just keep an ear on it and if it gets really bad then start worrying then.

 

[tomlegg]

Nice one will keep an eye on it and drive it harder as the noise is only at low revs!