1998 S500 Closing aid system
 

I have a 1998 S500. The drivers door no longer closes on its own any more. It makes a hissing noise and doesn't suck the door closed. What may be wrong with it? Is it an easy fix? Also the front passenger side door lock doesn't lock and unlock with the rest of the car. How do I go about fixing it?

Sounds (literally!) like you have a vacuum leak in the actuator. If you hear it hissing, it's time to pull the door apart and fix it. P.S. Sooner or later the closing assist pump in the trunk is going to log an error and stop trying to close the door. Don't worry. After you fix the leak , pull fuse #9 in the trunk's fuse panel to reset the pump.

Does the closing aid system have it's own actuator? Or were you talking about the door lock? Do you have any directions as to how to remove the door panel? I've removed the door panels on older mercedes but I assume this will be hard.

The closing assist and locking pump have thei own pump, the best article on close assist is
http://v12uberalles.com/
one pump is under the rear seat (lock) if only one lock does not work it is the line or element for that door. The close assist is in the trunk over the rear drivers side rear wheel.
I would do searches

Inside the door connected to the latch is a vacuum pod that pulls the door closed.
It is available & takes about 1.5 hrs to replace.