Could be the PSE vacuum pump. On our '99 C230K, it was the motor that runs the pump that died. Symptoms were inoperative central locking and non-functioning headrest drop. I think the motor and the pump are in the right side of the trunk. Have your mechanic check these two items first before checking the vacuum lines. Might save you some diagnostic time.

Here's a link to that discussion on my problem... http://www.peachparts.com/shopforum/showthread.php?t=164967

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ARVY

1999 E430
1999 C230 Kompressor
1992 300E (write-off)
1984 190D 2.2 (sold)