W124 diesels have a two-piece belly panel that screws to the underside of the car and covers the engine and transmission. In some of their writing (e.g., 1986 "Introduction into service," the factory claims that this is for reducing the drag coefficient. A couple of pages later, they say "On model 124.030 [gasser] the engine compartment is partially paneled underneath for improved aerodynamics." Later on that same page is a reference to "noise encapsulation on model 124.133 [diesel]."

EPC calls the belly panels "antinoise capsules" [diesel] and "engine compartment paneling" [gasser]. For diesels, the front one is 124 520 50 23 and the rear one is 124 520 34 24. Mechanics sometimes "forget" to put them back on because it saves them time when the owner returns for more service and many customers don't miss them. You might be able to get the panels from a forum member parting out a car but you don't want to know what the dealer would charge for a new one.

Incidentally, "merc" is a Mercury. If you want to use that kind of abbreviation for a Mercedes-Benz, use "Merz." And say "Sir!" And smile when you do it.

Jeremy

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970