I have an issue with a 2010 Opel / Vauxhall Insignia 2.0 CDTI Sports Tourer (aka Buick Regal in the States if I'm not mistaken) and I'm having difficulties pinning it down. It's going to be a lengthy read so I appreciate your time.
There is a strange clunky sound coming either from the engine or gearbox whenever I'm decelerating with the clutch engaged (engine breaking) or when I'm stationary with the clutch engaged.
When stationary, the sound doesn't always occur, however, if I repeatedly tap the accelerator pedal, it starts to make a rattling noise. This rattling noise only occurs if the clutch is engaged. Also, when engine breaking, if I disengage the clutch, the noise stops. Also, when pulling away in first gear from a stop, engaging the clutch also produces this noise. After the clutch fully engages, the sound seems to stop.
When accelerating, the sound either doesn't occur or is overpowered by the sound of the engine. I was never able to hear it when accelerating.
I've been having this issue since 2013 and at first it seemed this was only happening when the engine was cold but now it doesn't seem to make a difference.
I've since been to the dealership twice. The first time, they couldn't hear the sound (or probably just ignored my issue altogether), and the second time I took one of the mechanics with me on a drive to demonstrate my issue and at first they thought it was coming from the dual mass flywheel. They took it into the shop and then they said it was coming from the gearbox. They said they can't be sure what the issue is unless they take the gearbox apart. Since the car is second-hand and I'm not fully aware if the warranty still applied, I didn't go through with it since I didn't want to have to wrestle with them to do it under warranty.
I'm also reluctant to take it to the dealership again because, even though they are the least shady mechanics I can find, I once changed my brake pads myself in the driveway and a month later I went to the dealership to replace a torn hose from the intercooler to the intake and they claimed my one month old pads need replacing.
Once I have the time, I'll try and see if I can record the sound and post it here for you guys to hear.
I should also mention that I do not have any difficulty engaging any gear.
Until then, what are your thoughts on this?
EDIT: Here is the sound produced when tapping the accelerator pedal in neutral with the clutch engaged: Engine_Neutral_Noise
Now, this noise is really harsh and loud. The noise being generated while decelerating on the other hand, isn't as loud, it isn't as crunchy and its frequency is constant throughout the engine breaking period. Unfortunately, the mic was not able to pick up the noise while decelerating.