i just picked up a 1993 600SL.

when you start the car, there is quite a noticeable rattle, sounds and feels like you are driving through gravel.... it gets much quieter when shifting into gear, and gets louder again in neutral and park. Any clues?

It still runs very smooth and powerful except for these noises...and also it seems to be overheating after just a few minutes. bad head gasket? bad thermostat?

any help appreciated!