Vacuum Pump on W202

[David C Klasse]

I just tonight began to wonder if what I'm about to describe is out of the ordinary.
I unlocked my car via remote, doors unlocked, and the vacuum pump continued going for another good 5 seconds. The vacuum pump always stays on after the doors unlock/lock. I was beginning to wonder if this could be due to my vacuum leak in the unlocking air line (there are two, one unlocking/one locking in each door, correct?). My left rear door never unlocks like the others. It will hiss air and then a few seconds later will pop up, if at all. But it locks fine every time.
So what I'm asking.... Is my vacuum pump trying to equalize pressure or something from the leak in the line in the door? And if so, how should I solve this problem? I don't know how to get smoke into the system. Should I remove the door panel and possibly blow smoke at the area where it leaks to determine the exact location?
Thanks guys.

[MBenzNL]

There is only one line going in each door that will have an up going pressure (system blowing) to unlock the doors and will have a down going pressure (system sucking) to lock the doors.

If you hear a hissing sound in your rear door, there should be a leak. Remove the door panel and have a look (lock/unlock the car) and you will see/hear where the leak is. You do not need any smoke to find the leak.

greetingz,

[David C Klasse]

MBenz,
I did that once before, but could not find the exact location of the leak... I could tell kind of where it was coming from, but not exactly. So I might try blowing smoke onto it? I hope that will help me out. I'll try it again sometime this week. And the vacuum pump should not sound after the doors lock/unlock, correct?