Wonder if anyone can help. I've got a Vectra C 1.9 CDTi and over the last few weeks it's developed a fairly loud clunking sound whenever I go over speed bumps or potholes and even over drains. It doesn't appear to occur if I'm travelling at speed (although the roar of the road might be blocking it out) and if I'm travelling under about 20 then it doesn't happen either. Steering or braking aren't causing it from what I can gather.
It's a metalic-sounding clunk that is more obvious on the outside and definitely seems to be coming from the rear. Inside with the windows up I can hear a slight knocking, but it's much more apparent and metallic when the windows are down and I can hear it echoing off buildings when I'm driving down side-streets.
Took it to a local garage who said the only thing they could find was possibly the bumper was knocking against the chassis, so they tightened that but that didn't help.
Took it to Kwik-Fit today to get the whole suspension system looked at (fitted a new upper-offside rear arm after MOT a few months back) and they could see no problem in the stiffness of the shock absorbers, no leaks, no play in the bushes, no broken springs etc. They said they could hear the noise but couldn't work out where it was coming from - how annoyed was I?!
Thought the boot lid might be a bit loose, but after jumping up and down in the boot it wasn't the same sort of noise and it wasn't as loose as I'd imagined. Plus you would definitely hear that on the inside if that was the problem.
Have ruled out the exhaust (still tight on it's rubbers) and the heat shield isn't loose either.
At this point I'm pretty much out of ideas, apart from the possibility of the either the fuel tank being loose (I don't know if that's really possible or would make that sound) or something that's broken off in the fuel tank (again, I don't know what this could be and it seems unlikely to make that kind of noise - just exploring every possibility).
Anyone have any ideas? If not solutions then a list of things I can get the garage to check when I take it in again on Friday would definitely be helpful. Thanks in advance.