What steps can I take to diagnose a rattling noise?

[oldmanhouse]

Hi guys. My trusty (haha) Fiat Grande Punto has developed what I'd call a rattling noise somewhere in the engine bay or under the car, at the front.

It had a complete new exhaust last year, and I've taken it back to the fitter who informed me there's no problem with it. They patched a tiny leak in the mid-rear joint, and fixed a loose heatshield but that hasn't made a difference.

To me it sounds exactly like when my exhaust went last year (broken flexi pipe). But as it's been checked over and confirmed working, I'm not sure where to look next. Whilst they they had it on a ramp they checked the suspension too, and "all the obvious things" (wish I'd asked exactly what they were now).

I've got a few observations which might narrow it down a bit:

1. Rattle only occurs when in-gear and accelerating, or a little bit with the clutch depressed and I rev the engine.
2. More obvious when the engine is under strain (e.g. 5th gear at 20mph)
3. Haven't noticed any loss of power or lower MPG
4. Rattle is apparent at all speeds, but less noticable on the motorway due to road noise.

Apparently rubber mountings for the airbox can deteriorate on this model causing it to bang against a metal bracket, but mine seem OK. Then gave the engine a shove to test the mounts, and seems alright. Will jack it up at the weekend (weather dependant!) and have a look at the gearbox mounts.

Anything else I can check over? It's due a timing + aux belt, but doesn't sound like belt slapping, more metallic. No EML, so I presume that cat is doing its job still.

Edited by oldmanhouse on Friday 31st January 12:30

[Scrump]

As you can hear it with the clutch depressed then jack the car up (and properly supported) and get someone else to rev it whilst you look around in the engine bay and underneath.