strange flutter and pop of air from turbo when turning the car off, any ideas? 2.0 s-line 170

[arron1995]

today with the bonnet open when i switched the engine off i noticed a fluttering accompanied with a pop of air from the turbo, i took the inlet off and had someone turn the car off and sure enough when i put my hand infront of the compressor, it fluttered and then made a pop noise and shot air at my hand, im a bit confused as surely it should be sucking air not blowing it? is this normal, il attach a video, its a bit loud but you can hear it.  4 seconds in.

 

 

[cliffcoggin]

I have never noticed anything like that on mine, but then I don't turn off the engine with the bonnet open, so whether it is normal I know not.

I suppose if there is pressure downstream of the turbo when the engine is switched off the only way for the air to escape is back through the turbo. Let's hope someone else can chip in.

[arron1995]

1 hour ago, cliffcoggin said:

I have never noticed anything like that on mine, but then I don't turn off the engine with the bonnet open, so whether it is normal I know not.

I suppose if there is pressure downstream of the turbo when the engine is switched off the only way for the air to escape is back through the turbo. Let's hope someone else can chip in.

after watching some videos it seems the pop noise is normal, but the fluttering i have never heard it before and ive had the car since april and done around 15k miles, i never thought diesel turbos could flutter as they have no throttle body. this test was done with nothing connected to the compressor housing to see if it was due to the intake or breather and it was still present, i can only assume the air that comes back through is the air between the anti shudder valve and compressor itself so it must be air thats in the charge pipe.