I had to remove the OSF wheel arch liner today ( don't ask why ) and solved a nasty potential problem .

 

For some months now I could hear a funny "rattle" sound when idling with the A/C off, when A/C switched on the noise vanished. I remembered a discussion some years ago about the A/C pump pulley coming off, and the warning at the time to check the Torx bolt holding the pulley onto the shaft.

There were slight rust stains around the bolt head which made me check the bolt for tightness - at least one whole turn slack. A dab of Locktite and fully tightened proved a good move - no more funny noise.

 

It could be worth checking, you can see it with the skid plate removed, but full access with the liner removed.

good advice!