Technical Acceleration noise

[the drifter]

My 2005 2.8 Ducato based motorhome has developed a noise on acceleration. If I push the accelerator pedal sharply down you can hear a whoosh/whizzing(sorry for the description) sound above the ordinary engine sound.The turbo has been changed,the intercooler pipes disconnected also the aux.cam belt to the water pump etc but still the noise is there. The noise seems to be more on the o/s and rear of the engine. A local garage has had all its mechanics look but they cannot pin the noise down. If you keep the revs very high for a couple of minutes the noise seems to fade but as soon as you turn it off and restart it comes back. It seemed to start after the intercooler pipe had split and was changed (maybe a coincidence).
Any suggestions greatly appreciated.

 

[cris1117]

Hi. Your description reminds me of a job a few years back;from memory (which is not good these days) it was the rear cam belt cover(where it bolts onto the block) touching one of the pulleys.

I seem to remember one of the bolts holding the cover to theblock had worked loose, maybe you could upload a recording of the sound.

 

[DucatoMiltonKeynes]

If it isn't a mechanical fault of something like a pulley touching a cover, then the only other pressurised system is the exhaust/EGR/inlet manifold path. It might be a good idea to check eveything is nailed down nice and tight in that area.

 

[the drifter]

Thanks for the suggestions. Will check on cover etc and report back.

 

[cris1117]

Have you had a cam belt change or any work done in that arearecently?

Does it make the same noise with hot or cold engine?

 

[Arkk]

If you can definitely rule out intake faults like split hose (which is what it sounds like), then make sure it is not a partial exhaust blockage. What is an aux cam belt?

 

[the drifter]

In answer to questions raised :-
Aux cam belt -Sorry , belt that drives water pump and alternator. Briefly removed to eliminate these as source of noise.
Hot or cold-Noise is there both hot and cold. More noticeable when cold.
When vehicle is stationary the noise is noticeable when pulsing the accelerator.To make the noise stay on you need to be at nearly 3000rpm.
It sounds very similar to the noise heard when the intercooler pipe split.
The odd thing as stated is that if you keep it revving for a couple of minutes the noise will fade but restart it and it is back.
As stated the noise remains even after fitting a new turbo.
Have had a number of mechanics listen in the local garage, who all agree about the noise but can't find the source.

 

[the drifter]

Finally got problem sorted. It was a tiny split in exhaust manifold gasket.
Thanks for all the suggestions.