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Odd turbo noises...

9K views 53 replies 15 participants last post by  hamedhbb 
#1 ·
Lo all

Last week, I noticed an odd noise when lifting off the throttle after applying some power (i.e. quick start/rapid stop due to people in front slamming anchors on.

It's noticeable with the windows closed (more so open) and sounds (after you lift off) like "VVVV VVvv vvvv vvvv", definitely rotational, almost sounds like rubbing - and only when in gear (rev up/lift off in neutral doesn't do it) - so I suspected it might have been linked to the recently rebuilt gearbox - however the car went in for it's 1K post rebuild gearbox checkup today and that was fine - the chaps there had a drive/listen (bonnet up, throttle in gear) and it def sounds like it's coming from the lower right of the engine bay (when facing it) - is that roughly where the turbo is?

No power loss noted, but it wasn't doing it before last week, and is now.

Thoughts?

Crack(ing) hose? Turbo about to snuff it? Something else?
(Happy to pootle about if someone fancies a listen)
 
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#39 ·
Right then - car now back (following a 30 min Uber ride to go get it).
It apparently blew the induction pipe off, which has now been resecured....theory being that in trying to test for "the noise" it's gradually shifted the pipe, pinged the clip over the end and then the pipe end has popped off.

Errors cleared, it's driving again. Hopefully it'll behave now!
 
#42 ·
As long as it was nothing to do with the garage omitting to tighten it after the previous reassembly.:rolleyes:
 
#40 ·
Good news! Go and give it a blast. 😏

Sent from my Nexus 10 and a Black XF-S 😎
 
#41 ·
Hope this has sorted it for you, a bit of a journey.
 
#47 ·
Normally a turbo will have a blow-off valve installed, AKA dump valve or BOV, to vent the excess boost when you come off the throttle. This valve dumps the excess boost either back into the air intake (recirculating) or out to atmosphere - the latter makes a very distinctive 'tish' noise, also quite popular on modded cars. Most factory turbo cars have recirculating dump valves to minimise noise.

The cars in the video deliberately don't have one installed at all, so when they come off the throttle the excess boost forces its way back through the turbo, which stalls the turbo and makes a fluttering noise. That's what you hear in the video, and apparently it's quite popular in the modified car scene - even though it actually introduces more turbo lag. If the factory dump valve is stuck closed, you'd hear the same noise from any turbo car. It would likely be more muted on a factory car, but it would sound similar.

Hope that helps :)

Sam
 
#48 ·
It sounds more like the deleted/broken valve - it's "not quiet" but only does it when you are backing off the throttle in a hurry, and thus presumably needing to drop pressure.

I'm still keeping an eye on the car...I've had two Parkbrake faults since I've had it (cleared on restart) and one park brake failure - again reset on restart....
 
#50 ·
Hi sorry to dig up an old post, Did you get to the bottom of the issue? I’m currently experiencing the exact same symptoms on my car xf 3.0d
Thanks Sean
Read post #39
 
#51 ·
I got to the bottom of it by selling the car (it became an E350).

I suspect (in hindsight) it was a failed/failing wastegate/solenoid/something - the turbo was replaced and it was still doing it, and it vaguely sounded like those chavvy things that have dump valves rigged up (just muffled somewhere in the engine).

Shame, as I did like the XF - looked lovely and was v comfy, but I suspect I just acquired a lemon...
 
#53 ·
Thanks for the reply. It wasn’t a 2010 xf in grey was it?🤔🤣 Can I ask how long you drove the car whilst it made the noise? I definitely think I have the same problem from what you have described. I can hear the air coming back towards the inlet side from the turbo. Cheers Sean
 
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