Engine rattles when idling

Can you provide us with more information? What did he check?

You've given very little information to go on. But, just in case, here's a thought:

My 97 SL2s used to rattle at idle. It was the headlights. When you're idling and rattling, press gently on both headlights. If the rattle stops, then it's probably the tongue in grove joint for holding the headlights in place. A bit of silicone RTV will fix the rattle while remaining pliable enough to adjust the aim of the lights.

Good info. I have a 97SL2, it rattles when cold and idling. The sound is very metalic, but goes away when warmed up. I read this rattle was mentioned in the review of the car when it was first new. So just learned to live with it.

later,

tom @

This was actually one of the first little repairs I had done on my '98 SL2, they tightened a few bolts around the headlight fixtures and bang, no more vibrations.