"pinking" noise in 2.0d
 

My new 2.0d V70 is making a sound very much like pinking (I thought that only petrol engines pink) It happens under moderate throttle/load between about 1500 to 2500 rpm. The volume of the noise is directly proportional to throttle position - more throttle louder noise, foot off, no noise. Even on cruise at a steady speed you can hear the noise come in when you go up an incline. Once you get above 2500 it pretty much goes. It does not seem dependant on temperature (not that I can tell as there is no temp guage on new V70s) but it happens from a cold start or when the car has been running for hours in the same way. Its pretty loud and can be heard easily over the radio. It is accompanied by a kind of whistling sound, almost as if the exhaust is blowing but as it very quiet when not on the throttle or even at higher revs I can't imagine its that. Anyone got any clues? Its going in for its 3000 mile "quality check" service next week so hopefully they will sort it but I wouldn't mind getting some points of view beforehand.

If it’s the noise I’m thinking you mean I had this a lot when I first got mine. It’s not pinking it’s labouring your in too higher gear for the speed your doing. Used to do that a lot in mine when I first got it. The last diesel car I had was VW Bora TDi you could lose a bit of speed in that and still hold onto the gear and I kind of thought the V70 would do the same. No any remote loss of speed and you generally need to come down a gear. I also found that it needs to be in a gear lower than you think most of the time and now I’ve got the knack the MPG is actually starting to improve. Remember it’s a heavy car and not really that powerful.

I wouldn't have said it was a labouring noise although I know what you mean. It doesn't like to pull between 1200 and 1500 revs and if you try in those revs it does labour. The turbo starts to spin (audibly) from about 1350/1400 after which it pulls strongly and the labouring noise/vibration (which I would avoid generally anyway) goes away. After a brief spell of pulling cleanly and strongly mine starts to make this "pinking" noise that is worse with more throttle/load (as I agree labouring would be) but it continues right up to around 2500rpm. I can't imagine that any engine should still be labouring at this kind of rpm as it is right up high on the torque curve from 1800. Whilst I have described the sound as a pinking noise (as it is very similar to a sound made by a petrol car I used to have years ago when first using unleaded before retarding the iginition sufficiently) but it also sounds a bit like the exhaust blowing, or maybe the manifold - I'm guessing the pressure in both is highest in this range.
The other reason why I think this is a problem with this car (as opposed to my driving) is that the test drive car I borrowed for 24 hrs/300+ miles didn't do this at all. Regarding the heavy car/relatively low power thing my last car was a 2.0d A6 so was broadly similar in this respect but never made a noise like this.
Its going in tomorrow so hopefully they will find something and fix it.

Update on this post, in case anyone else has something similar. It came back from the 3000 mile check unsolved - they (Johnsons of Gloucester) said it was perfectly normal. I mentioned it again when booking it in for my 12,500 service which was done yesterday by MRG in Chippenham. MRG obviously checked it out properly as they discovered a "loose intake chamber to turbo" Not sure exactly what that is but I believe its some kind of plenum. They said the bolt that should hold it tight was missing altogether. as the pinking noise hasn't altered since the car was brand new I'm guessing this must have been the case when it left the factory. The car is much quieter and smoother pulling in the 1500 to 2500 rpm range so is now what it should have always been. I'm a bit unhappy that it wasn't sorted sooner but I'm pleased it is now, and that I wasn't being daft being concerned about it. Thanks very much MRG if you are out there! Highly recommended.