My BLT VRS is starting to act a bit weird and its pretty hard to explain.

After a short while of driving, the turbo will start to sound like its making boost on de-acceleration / engine breaking when i lift off the throttle and slow down. Its only started doing this recently and its quite noticeable.

If i drop the clutch to drop the engine speed to idle the noise instantly stops.

If i stop turn the engine off then restart the boosting sound will go away then return again after a few miles or so.

Any one else had any similar problems?

By making boost do you mean you can actually hear the turbo spooling up. By this I mean can you hear it whine like under acceleration? Or do you mean you can hear the sound of boost pressure being wasted on the overrun?

Forgot to mention you will need the windows down to hear it whine as it spools up.

Also forgot to ask. Have you checked all your vacuum hoses for leaks and checked pipe work on the high pressure side of the turbo for boost leaks? You should know if there are any issues there because the engine will be sluggish and lacking power but it's worth checking still.

Yes can hear it whine, like it does on acceleration. No where near as loud, but very noticeable even with the window up. Doesn't sounds like is leaking boost, its driving fine and pulling as hard as it did before.

I've been poking around abit more on the internet, and it mite be EGR related. As its the same noise i get just after start up where it sounds like its making boost / whine but that then goes away after the first blip of the throttle.

Going to pull the vac lines and check the turbo actuator working freely tomorrow, was hoping some other people had experienced this issue.

I'm wondering if you have a turbo actuator or vacuum problem. Under overrun conditions in most standard diesel engines the actuator will open a waste gate or bypass valve to allow excess boost pressure to leak off through to the exhaust. On overrun this may be a constant slight opening of the bypass valve, because the actuator needs to maintain compressor wheel speed so that throttle response will be higher when accelerating again. The actuator is normally closed by a vacuum supply and opened up again by excess boost pressure. If your actuator is not opening properly then it may not be allowing enough boost to waste away. This will keep your turbo speed too high on overrun and could cause your noise with it spooling up / producing boost.

Been doing some more investigation and the car is definitely maiking boost on run down. Its showing around 4-5psi on the scan tool when it should be showing a negative vac. Could this be sticky vnt/wastegast causing this. It generally happens more after a hard drive.

Edited 22 June, 201610 yr by kellaway86

Been doing some more investigation and the car is definitely maiking boost on run down. Its showing around 4-5psi on the scan tool when it should be showing a negative vac. Could this be sticky vnt/wastegast causing this. It generally happens more after a hard drive.

 

4-5 psi is a vacuum, atmospheric pressure is 14.5 psi. Also the VNT does not have a wastegate.

Im not to clued up about the way it works. It shows no boost at all when its making the normal noise on run down just shows a vacume. When it start making the boosting noise its showing 4-5psi of positive pressure. Which to me is madness as it should only be making boost on acceleration.

Sounds like a sticky vnt to me