Water got into my 87 300e under and behind the driver's seat and backed up into the channel under the left side of the rear seat where the wires from the trunk are bundled. Now the pump under the left side (driver's side) of the rear seat makes chugging or clicking sounds; previously it was silent. What does this pump do, and what should I do? Thanks.

__________________
87 300e (white/black; amg body kit)
88 300ce (red/cream; amg body kit)
93 300ce cabrio (white/blue/blue top)
93 300ce cabrio (black/grey/black top)
98 ml 320 (totaled @ 137,000 miles)
99 clk320 (black/grey/black top)