Slight whistling sound under acceleration

[noetus]

I've noticed that my 2.5 TDI is whistling slightly under acceleration. I guess this is the turbo but I'm not sure if the sound is normal or something I should worry about. I only hear it with the windows down and it's only really noticeable when accelerating on narrow country roads where the engine sound reflects from the side of the road (grassy banks) back into the cabin more readily.

Can any 2.5 TDI owners shed some light on this? With the windows down and some spirited driving on country roads, how much turbo whistle do you hear? If "none" I guess I might be in trouble but if "a little, some" then maybe not?

[Guest 2]

Do a quick visual inspection of your pipes.

Both my cars have a faint whistle under acelleration so I think it's normal.


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[mikeybutch]

My last 2.5tdi had a distinct whine or whistle whereas the current one nothing until my son put a spare cone air filter on and now gives a loud whoosh which has taken some time to accept.Still might change back to the original.As with most strange noises I like to wait and see if they vary and if not live with them.However I know some cant and must investigate every rattle

[noetus]

Before starting an investigation of hoses etc I'd like to add the following information which may help someone zoom in on the issue.

- The whistle is only noticeable when (1) the windows are down and (2) the care is under acceleration and (3) the road has banks, either grassy or concrete, that reflect the engine noise back into the cabin. If there's a vacuum leak it must be a small one I reckon.

-Today I was listening to the whistle and suddenly it seemed to stop - halfway up the hill I was accelerating up. So perhaps it's a bit intermittent, which could maybe indicate a hose?

- It seems to get slightly louder when I lift off the accelerator to change gears, almost like there's a wastegate (there isn't one though).

- Recently I've noticed slight amounts of hesitation in power delivery here and there, mostly at higher revs

- The car's computer appears to be pessimistic about average mpg. It's saying 33 but from careful measurements at the pump I reckon 35.

Does this combination of symptoms help narrow it down?

[mikeybutch]

I never found what was causing the noise on my earlier car butthere was probably something amiss.It never changed or affected performance so I accepted it .It could be turbo related if the vanes are dirty.DIS always varies from true mpg

[Alan02]

As mentioned check hoses etc from Turbo, including Intercooler, but dont rule out the Intake manifold gaskets/security need checking too if no other defect found.

[bobfish45]

My 2004 Quattro 2.5tdi whistles around town at low speeds,though it disappears when revs and speed build up.