D3 Strange noise from engine bay

Thanks for the input Old Salt.
I haven't been able to find anything in the way of tools in the engine bay & the mechanic had a quick look after he finished the service but couldn't find anything & reckons he not missing anything.

Thanks Terry for your thoughts .. there was initially a suggestion from the mechanic that it may have something to do with the auto transmission (torque converter) but the AT has been serviced (steel pan & flush) and seems to be very smooth changing up and down effortlessly. I did notice for a very short time that the noise went away after the old alternator was replaced with a new one .. but the noise is back.

Sniegy, I will give this a try but could be tricky as the noise is only heard whilst driving. If I try to replicate the noise whilst stationary there's no sign of the 'noise' at all.

Thanks for your thoughts Connock .. it only happens at those revs whilst driving.

Thanks Justinc. Now you mention it I will investigate this. Actually our Td5 had a problem with an idler arm pulley which was making a weird noise. It eventually seized and left us stranded for 24 hrs out the back of Lithgow.

Ours mainly makes the noise when the engine is under load when driving, it also happens occasionally on over run when you just lift your foot off the gas for a second or two.

I too wondered about the belt tensioners and pulleys, but they were checked and one replaced, which did improve it for a while I must admit.

cheers,
Terry

My 08 RRS TDV6 makes the cicada noise in exactly the same circumstances as Terry has described. Under load around 2500rpm and briefly on overrun sometimes. 163K on the clock and just getting parts required to do timing belt (I enjoy doing my own mechanical work), so I'll inspect all the pulleys when I remove them.

I had a new timing belt fitted only 10k ago so that shouldn't be the issue, does sound more and more like the pulleys/tensioners.

cheers,
Terry

Mine does the same.... It has done it since I got it 40K back.

Haven't been able to find anything. New motor 50K ago, transmission rebuilt 10K ago.

I thought it might be one of the shields underneath vibrating.

Hi austeve01,
Just a thought, when you had the alternator replaced did you also replace the serpentine belt? I had a similar issue on my wifes car, when the alternator was replaced as part of a battery that was less than serviceable event. When the alternator was replaced a noise that was there before disappeared and then returned a couple of weeks later, I replaced the belt and re tensioned (no auto tensioner) the belt and the noise never came back. Just an idea.