What's up with the "flaps"?

[Chris W.]

On my new (to me) '95 E300D, I finally had a chance to get up under over the weekend, doing an oil change, etc. Pulled the belly pan, and on either side of the area where the belly pan edges are, are a set of black plastic "flaps" which have some sort of spring loaded actuator. These appear to be for ventilation of the engine compartment?

On my car, the driver's side flap unit was flopping loose, missing a fixing screw, and the flap actuator gizmo was so stiff I could hardly move the flaps for fear of breaking them. The passenger side set was properly fixed and the flaps were "openable" but quite stiff.

Can someone shed some light on how these things are supposed to work? Is what I call the actuator some sort of thermal spring or something? I can't see any condition which would cause them to open other than temperature, i.e. not just air moving thru them.

I also see that I need a new belly pan - I guess I should be happy that I have one at all after reading the other thread about them. Mine is rather trashed.

Rgds,
Chris W.
'95 E300D
'93 500E