Mercedes W123 Central Locking
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  1. #1
    Fellow Frogger! Boyracer's Avatar
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    Default Mercedes W123 Central Locking

    Hi All,

    I realise this is a website for French cars, but I've posted this on the MB club site and had absolutely no response. Presumably no one has the first clue. Posibly they're just not interested. A large part of me wonders whether some of them would even recognise their own car if you took the three pointed star off the bonnet... 'this can't be my car. My car has a star on the front!'

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    I'm told the Pug 604 has the same system, so... is that a good enough excuse to post this here?

    Anyway, I know there are some knowledgeable folk on this site. So, please help if you can. This car is now driving us nuts!

    My dad has had this car since new (1985) and early this year had problems with the central locking. Namely, it only works if you lock the doors as soon as you switch off the engine. The dealer 'fixed' it during the last service some months ago (I think they replaced something called an actuator in the driver's door), but it has stopped working again this week.

    If you wait more than say 15 seconds, it seems there is no longer sufficient pressure in the system to lock anything except the driver's door which is locked mechanically anyhow.

    At this point, you might try going around and pressing each button down manually, only to see out of the corner of your eye other buttons move themselves back up as you do so! And on a couple of occasions, some doors actually managed to unlock themselves whilst the car was left unattended.

    I've opened up each and every door and checked the little chambers for leaks. They all seemed fine. I'm frustrated and I'm going nuts.

    Has anybody got some pointers for me?
    Last edited by Boyracer; 2nd October 2005 at 10:08 PM. Reason: Grammatical Error
    Cheers,
    Michael

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  2. #2
    rek
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    Default

    We used to be a Mercedes family, my mother owned a W124 with a very similar central locking problem. As far as I remember, it was such a pain in the arse to deal with time and again, we just gave up on the idea of working central locking.

    Nothing more to add, except I LOVE the older Benzes. The environmentally-incorrect bastard in me longs for a 450SEL 6.9
    Peter
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  3. #3
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    There are plenty of Mercedes forums, but the W123 is a bit old. You could ask at:

    http://forums.mbworld.org/forums/index.php?

    There is a W123 subforum here:

    http://www.benzworld.org/forums/default.asp

    I did a central locking search for you but I htink it will be easier for you to search for a thread that is helpful, view the search results here:


    central locking search

  4. #4
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    Quote Originally Posted by rek
    We used to be a Mercedes family, my mother owned a W124 with a very similar central locking problem. As far as I remember, it was such a pain in the arse to deal with time and again, we just gave up on the idea of working central locking.

    Nothing more to add, except I LOVE the older Benzes. The environmentally-incorrect bastard in me longs for a 450SEL 6.9
    The 450SEL 6.9 sounds very disappointing though, all breathless fan type noises Sure it can be recitified though!

    I love the W124, especially the updates, an update E280 or E320 would be very nice Hope to have an AMG one day though...

  5. #5
    Fellow Frogger!
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    Default locking

    you will probably find the hoses to the actuators are perished,
    most likely on the ends or junctions as it works on vacuum
    and you have a leak
    to find it you may have to trace all the lines but I would begin with the joins
    remake the connections if they are perished buy cutting them out and rejoining
    good luck
    Alpine

  6. #6
    Fellow Frogger! Boyracer's Avatar
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    Thanks guys. Sounds like some tedious sledding is ahead of me. I guess I know how I'll be using the extra day of my long weekend... I wouldn't mind so much if I was confident I'd find something. Fingers crossed!

    Putting my froggy obsession aside for two seconds, I don't mind some of the older Mercs. Definitely like them a whole lot more than the new ones!

    Sergetov- Thanks for the links. After looking through the posts, it seems this central locking leak is of pandemic proportions! Quite a few people seem to have the same problem. I finally found a recipe for leak troubleshooting and have copied it if anybody else here needs it.
    Cheers,
    Michael

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  7. #7
    Fellow Frogger! 306XT's Avatar
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    Nothing to do with the lock, but my family had a 300E the generation after yours & they really were pretty good (I especially remember that merc exhaust note). Then we move up to a 500SEL (the 90s ones) NOW that car is also utterly environmentally-incorrect. But that thing was huge (I was like 12 at the time, its like moving your lounge into a moving thing)

  8. #8
    Fellow Frogger! 604 tragic's Avatar
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    Quote Originally Posted by Boyracer
    Thanks guys. Sounds like some tedious sledding is ahead of me. I guess I know how I'll be using the extra day of my long weekend... I wouldn't mind so much if I was confident I'd find something. Fingers crossed!

    Putting my froggy obsession aside for two seconds, I don't mind some of the older Mercs. Definitely like them a whole lot more than the new ones!

    Sergetov- Thanks for the links. After looking through the posts, it seems this central locking leak is of pandemic proportions! Quite a few people seem to have the same problem. I finally found a recipe for leak troubleshooting and have copied it if anybody else here needs it.
    Its easy to fix - as its probably the bellows diaphram rubber in the RH rear door (at least thats where they go on the 450's).

    Take off the door trim and get a bit of tube/hose to test each (just use sucking/blowing & you will soon see which is good or bad.
    Each door has a double set of diaphrams - one to open & one to lock - they operate on vacuum through small tubes. If one rubber is perished you get exactly what you have described as the vacuum leaks out quickly after the engine is turned off.
    These are available & Benz dealer spare parts prices are far less than Peugeot/Citroen (for the same thing) or theres usually a non-official parts place that will post them - like that Green bloke in Canberra.


    IMHO its easy to replace on a Benz & hard in a 604
    So many projects - so little time.

  9. #9
    1000+ Posts Wildebeest's Avatar
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    Default Central locking.

    One of our PCCWA 604 owners gave the vac operated locking system the "BIG A" and replaced everything with a cheap electric,[Tandys, Dick Smith] system. He claimed it was no big deal to install.

  10. #10
    Fellow Frogger! Westair's Avatar
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    Quote Originally Posted by Boyracer
    Thanks guys. Sounds like some tedious sledding is ahead of me. I guess I know how I'll be using the extra day of my long weekend... I wouldn't mind so much if I was confident I'd find something. Fingers crossed!

    Putting my froggy obsession aside for two seconds, I don't mind some of the older Mercs. Definitely like them a whole lot more than the new ones!

    Sergetov- Thanks for the links. After looking through the posts, it seems this central locking leak is of pandemic proportions! Quite a few people seem to have the same problem. I finally found a recipe for leak troubleshooting and have copied it if anybody else here needs it.
    This is a forum for old MBs inc a 123 section- it was part of http://www.mbz.org but you will find this quicker.

    http://forum.mbspares.com.au/

    My 114 had same problem and it was just vacuum pipe in LH fron door. Just sealed another plastic tube with ID same as OD over broken section.
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  11. #11
    Fellow Frogger! Boyracer's Avatar
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    Thanks guys,

    I think I've found the leak. Looks like an actuator in the rear passengers door. the system seems to work fine once this actuator is taken out of the loop. (Good call, 604 tragic!)

    I'll give the dealer a call in the morning and hopefully pick up a part during my lunch break. Fingers crossed they have it in stock!
    Cheers,
    Michael

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  12. #12
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    Quote Originally Posted by Boyracer
    Thanks guys,

    I think I've found the leak. Looks like an actuator in the rear passengers door. the system seems to work fine once this actuator is taken out of the loop. (Good call, 604 tragic!)

    I'll give the dealer a call in the morning and hopefully pick up a part during my lunch break. Fingers crossed they have it in stock!
    Looks like you may have already found the problem.
    If its still there, look for the main reservoir - it looks like an egg-crate and I think is mounted just behind the left front wheel behind the mud guard. There will be a one-way check valve between the engine vaccuum and the reservoir. If the valve is leaking the reservoir will empty shortly after the engine is shut off.
    I also remember on some models (diesel?) some of the pvc lines ran near the battery and were prone to getting holes eaten into them by the battery acid.

    Also, there is a very useful tool for future diagnosis - it is a hand operated "gun" shaped vacuum pump with a small vacuum gauge attached. You tap into the section you want to test, pump it until the vacuum builds up, and the gauge tells you whether that area is leaking or not. Should be fairly easily available .

    Good Luck
    Fordman.

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