steam cleaning makes the engine bay "like new". as you may have surmised, the only concern would be the electricals. anybody reading this with a '93 - '95 w124 take note. if you have not had your wiring harness replaced don't even think about it! i've had mine replaced and i still won't ever have mine steam or any kind of water cleaned even though i would do it on other cars without hesitation.
1993 300e-2.8 - gone now <sigh>
"Do not adjust your mind, it's reality that's malfunctioning"