Hissing in driver's door lock
11-20-2017, 01:54 AM
#1
Hissing in driver's door lock
Hello all, have what might/not be a problem. First let me say that the lock functions in the wife's '98 C280 Sport work like they should, locking, unlocking, remote, etc.
However, if I sit in the car and use the key fob to lock the doors, there's a hissing sound coming from the driver's door lock area. I can also hear the vacuum pump humming for maybe ten seconds, which I believe is normal. The door locks as it should. I haven't searched exhaustively for functional characteristics, thinking some wizard will simply say "it's this and you have to that..."
I would rather not go into the door and mess with it since it's working, but if the hissing sound means there is a leak, then it will eventually fail and I might as well go there and deal with it. If I used a vacuum gage (somewhere) what is the level of vacuum I should see in the system when there is no demand? Is there supposed to be vacuum in the system at rest (does the vacuum pump actuate only when needed, in which case a zero vacuum reading would indicate no vacuum and okay, or should there be "reserve vacuum" in the system at all times, augmented as needed by the pump?
Thanks!
However, if I sit in the car and use the key fob to lock the doors, there's a hissing sound coming from the driver's door lock area. I can also hear the vacuum pump humming for maybe ten seconds, which I believe is normal. The door locks as it should. I haven't searched exhaustively for functional characteristics, thinking some wizard will simply say "it's this and you have to that..."
I would rather not go into the door and mess with it since it's working, but if the hissing sound means there is a leak, then it will eventually fail and I might as well go there and deal with it. If I used a vacuum gage (somewhere) what is the level of vacuum I should see in the system when there is no demand? Is there supposed to be vacuum in the system at rest (does the vacuum pump actuate only when needed, in which case a zero vacuum reading would indicate no vacuum and okay, or should there be "reserve vacuum" in the system at all times, augmented as needed by the pump?
Thanks!
11-20-2017, 11:34 AM
#2
Super Member
Its a door lock actuator inside the door panel near the latch.. Probably busted or cracked at either a vacuum line or the actuator itself. Does the door lock seem slower than any of the other doors when you lock it?
But yes, you will have to remove the door panel to get in there and see the root cause of the issue. More than likely its the actuator, but I have seen the vacuum lines break near the wiring harness passthrough at the front of the door near the hinges.
Good luck
But yes, you will have to remove the door panel to get in there and see the root cause of the issue. More than likely its the actuator, but I have seen the vacuum lines break near the wiring harness passthrough at the front of the door near the hinges.
Good luck
11-20-2017, 02:43 PM
#3
Thanks much, Racin_fool, it's pretty much as I expected. At this time since that lock works adequately I can postpone the repair for another day, or when it gets worse.
11-21-2017, 10:06 PM
#4
Now then, back to part of what I originally asked: is the vacuum system supposed to hold vacuum when not in immediate use, or does the pump come on and supply vacuum when needed?
In the first case, the pump runs when the system is used AND vacuum drops below a certain level; in the second case the pump runs every time a device is used. The import of this is that if I have a leak, is the pump working more frequently because of it, implying that rather than risk a costly pump replacement, I should spend now for a replacement door actuator? That's where the money hits the road... besides I don't want to go into the door until/unless it's needful.
In the first case, the pump runs when the system is used AND vacuum drops below a certain level; in the second case the pump runs every time a device is used. The import of this is that if I have a leak, is the pump working more frequently because of it, implying that rather than risk a costly pump replacement, I should spend now for a replacement door actuator? That's where the money hits the road... besides I don't want to go into the door until/unless it's needful.
