Strange Engine Sound

[lifeline830]

Recently I have noticed a strange slight rattling metal sound when my engine runs at around 1000 RPM, more noticeable in reverse. The sound is heard best when passing objects on either side (for sound reflection). I have no idea what it could be. Does anyone know what this can be?

[MazdaSpeeder]

Could it be a loose heatshield? My resonator heatshield rattles at about 2.5k rpm. Give us more information...is it only at 1k?

[jeg0024]

I have a missing small ass nut on the heat shield on the radiator fan and it rattles sometimes at low rpm's. Any other heat shield would give the same kinda noise though, check all your nuts!