Turbo noise?

[Ollie795]

Hi everyone,

Ive got an Avant quattro with the 2.0TDI 170 PPD engine, when accelerating with only a little throttle I get this strange noise from the turbo, it's almost a mix of a rattle/spooling noise or like the turbine is dragging on the case of the turbo but i'm sure if this was the case I would have a lot of problems, I have no over boost issues etc just this strange noise, when I let off the throttle quickly when going up a hill (so high boost) it does the turbo flutter noise but with the same rumbly sound, which I understand is effectively excess pressure produced by the turbo that isn't needed, is it possible that my car is very slightly over boosting on light acceleration? I have had the intake pipe off and checked for play in the bearings, there is some side to side play but not excessive and a very very tiny bit of end float so I don't think it's the turbine shaking around, could it be the variable vanes sticking? car is on 123k miles

[tc95397]

Boost leak probably on intake manifold. I have this exact issue but only when its hot outside (that suggest its on metal-metal coupling).If intake manifold is bolted on correctly and gasket is ok then I would look into leakage around some rubber intake pipes.

The sound you are describing is in fact a little weird because it sound almost like "dragging" but its just air either under manifold gasket or some pipe.

[Ollie795]

I've had the manifold and EGR off recently and fully cleaned it and set the adaptations for the EGR valve that cured a general lack in power, I think due to the EGR being out of position and also everything being so sooted up! Im happy there is no leak around the manifold other than a tiny one out of the swirl flap spindle but there is very little oil build up around it so i'm not concerned with that, this didn't change the strange noise in any way.

I've had the turbo outlet hose off to replace the engine mount and had a good look at that, no splits, and i've checked the rest of the hoses fairly well with no obvious signs of a boost leak (have dealt with many on other cars before) I haven't been able to check the intercoolers, are they a common failure? 

I don't get any black smoke from the exhaust under hard acceleration admittedly it is a DPF version but theres not even a hint of smoke in the headlights of a following car with the lights on with full acceleration, which would usually indicate over fuelling due to lack of boost.

Have driven the car quite a bit and theres been no change in the noise so i'm not overly worried about it just curious as to what it is, never heard it on any other turbo car i've had