for some reason, my brain is telling me that "MKE" port services the ortho seats.
if your pump is same as my 99 E320, it would be lower right corner.

check pump outlet for air
check hose leading to front seats air control module for air
pop off rear seat cover and check for air leak at the connectors

....and hope that it isn't in the air bladders themselves. but the manner in which
you're describing the total lack of function at all air bags, i'm thinking it something
further upstream towards the pump.

the air hoses can become hardened and fail, especially if previous owner had
man-handled them

__________________
-- raymond~
47º 34'N 122º 18'W