Turbo noise when cold at 1500 RPM?

[vwengineer]

Hey!

Just discovered a new noise that I am not particularly fan of. Started the car today, temperature was 4C, drove gentle as usual but I noticed that at around 1500 RPM (out of boost so) if I gave say more than ~40% throttle there is some kind of howling/whining sound coming from the passenger side.

The noise is not really high pitched, it's smooth and follows exactly the amount of throttle (but disappears if throttle is not at least 40-50%). I don't know if a turbo make this sort of noise before giving up? The sound disappeared after 2 miles.

I run 5W-30 oil so it should flow OK at this temperature.

Anybody experienced something similar? What would you do in this situation?

 

[golfballer78]

Does it run any different other then just making noise? Power loss?

 

[vwengineer]

No, it seems to run fine. I took VCDS and looked at turbo pressures, actually it seems to boost a bit a this level of throttle which I didn't think initially (0.4 bars). It is in-line with requested pressure generally and maximun N75 duty cycle is around 45% which I seems normal (but that is with a warm engine).

 

[golfballer78]

Boost leak at one of hose connections maybe?

 

[vwengineer]

Yes could be, but the fact that it disappears quickly is strange. Might be a leak on the exhaust side though (that seals up with temperature). I will try to do a smoke test although I am not sure something would show up since I have no way to really pressurise the exhaust.

 

[golfballer78]

Could look for cracks in the manifold/hot side of the turbo area. Or if the flange gasket to downpipe leaks, spray copper coat on that gasket & reinstall, or get new one.

 

[vwengineer]

Ok, I will have a look. Thanks!