w124 cabrio understanding the hood mechanism

Discussion in 'Bodywork' started by rigel, Oct 4, 2011.

  1. rigel

    rigel Hardcore MB Enthusiast

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    Greetings all, I am looking for a little light bedtime reading regarding my W124 hood mechanism.

    I would love to understand the process of how my hood works after I unclip the front head catches and press the illuminated red button.

    How does it all orchestrate together? Does every moving part have open and closed sensors? Where are the brains? Is it Ok to stop halfway through the process to work inside the hood bay?

    I know the power is supplied from the pump in the boot and there are a row of what seem like valves hidden in the hood compartment above each wheel arch, but what governs it all and how does it know when to push and pull which bits?

    Would love to get my head around the process and also learn how to do routine maintenance to keep it moving smoothly.

    Is their a MB guide/worksheet anywhere out there that covers checking, realigning and maintenance of these exquisite mechanisms.

    Thanks in advance for any illumination that can be shed.

    Regards. R
     
  2. BillyW124

    BillyW124 Hardcore MB Enthusiast

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    I dont specifically know the answer to your question as i dont own a cab..maybe one day! But im sure the likes of WDB, The boss and a range of others with vast knowlegde will!

    We are not mad we are not crazy we are damn right nutty! 124 :rock:
     
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  3. OP
    OP
    rigel

    rigel Hardcore MB Enthusiast

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    Thanks Billy.

    I too am hoping some of the senior (more knowledgeable) members have some information tucked away somewhere that they are willing to share.

    Regards. R.
     
  4. Alex Crow

    Alex Crow Hardcore MB Enthusiast

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    Yes, there are limit switches to detect the end positions of hood bow, cover and front frame, as well as locked/open switches to ensure all catches are doing as they should. Obviously this system has to be pretty good to avoid the hood chewing itself to pieces on the compartment cover! In addition there is a temp sensor in the pump unit, as well as communication with other module/s on the car to check vehicle speed (you do not want to try dropping the roof at 100mph!) etc.

    The control module is under the rear seat.

    You can stop the roof halfway, but beware, it will only hold in position for a short time before the hydraulics are released and it drops forwards or rearwards depending on position. With care and ingenuity you can hold it in an intermediate position if you wish.


    I should say that some details above may be incomplete or inaccurate, there are some dedicated W124 enthusiasts here that will add a little more no doubt.
     
    Last edited: Oct 4, 2011
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  5. OP
    OP
    rigel

    rigel Hardcore MB Enthusiast

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    thanks Alex.

    is it Ok to change the direction of the hood before it has reached the end point of its initial direction?

    ie, from closed position to toneau up and bow up, to back to closed position without folding the hood away fully first?

    regards. R
     
  6. BlackC55

    BlackC55 Authorised Forum Sponsor Authorised Forum Sponsor

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    Yes it is. It does not have to do a complete cycle.

    The hydraulic system is very complicated. When the rear seats are removed the pipework is truly amazing!

    The roof on the 124's is generally very very reliable.
     
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  7. OP
    OP
    rigel

    rigel Hardcore MB Enthusiast

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    hi Olly, thanks for that.

    seen all the piping and wiring when i had the rear seats out myself, and am amazed at the complexity hidden within.

    do you know if there are any general maintenance projects that i can do to keep it working smoothly? does it need lubing anywhere?

    regards. R
     
  8. RBYCC

    RBYCC Hardcore MB Enthusiast

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    The only maintenance required is making sure your hydraulic resorvoir is always full.
    Exercising the hood on a regular basis tends to keep the seals soft.
    The A124 has eight hydraulic cylinders and in time they will leak as the seals deteriorate...

    The below link is to an extremely important service instruction, much better then any issued by Mercedes.
    It was done by a member of a USA Merc forum.
    In the USA the Mercedes OEM hydraulic cylinders can amount to over 3500 sterling for the eight units.
    Rebuilt with advanced seal material the cost for all eight is about 300 sterling !! ;)

    http://www.tophydraulicsinc.com/E320 Hydraulic Cylinder Removal Manual.pdf
     
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  9. Dee-124CAB

    Dee-124CAB Hardcore MB Enthusiast

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    Where and how does one access this hydraulic reservoir to check and top up fluid?

    Is there a dipstick type thing?

    Dee
     
  10. OP
    OP
    rigel

    rigel Hardcore MB Enthusiast

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    Hi Dee,

    The hydraulic reservoir is in the boot, on the driver’s side behind the boot lining under the metal cover.

    There is a fluid level on the reservoir that can be seen with the boot lining removed.

    i don’t know if it is prudent to change this fluid at some point or just keep it topped up?

    it works all the hydraulics for the roof mechanism, so a lot is dependent upon it.

    Regards. R
     
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  11. OP
    OP
    rigel

    rigel Hardcore MB Enthusiast

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    thanks RBYCC,

    thats just the sort of reading material I'm looking for.:thumb:

    regards. R
     
  12. Stratman

    Stratman Hardcore MB Enthusiast

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    Are there interlocks on the catches behind the sun visors?
     
  13. Scott_F

    Scott_F Hardcore MB Enthusiast

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    So if you remove the boot lining and the metal cover can you check the fluid level and top up the reservoir from inside the boot ?
     
  14. scillyisles1

    scillyisles1 Hardcore MB Enthusiast

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    yes
     
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  15. OP
    OP
    rigel

    rigel Hardcore MB Enthusiast

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    Does anyone know if the hydraulic fluid in the hood mechanism should be changed? or is it Ok to just keep topping it up?

    regards. R
     
  16. Alex Crow

    Alex Crow Hardcore MB Enthusiast

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    Hello R,

    No, it does not need changing - OR topping up!

    If you find that is is losing fluid you have a leak, and this should obviously be fixed.


    The reason it does not need replacing is simple enough, the fluid has a very light work load.
    Hydraulic fluids in e.g. power steering applications are in constant use, all the time you drive. The hood however will barely rack up 24hrs of run time in its life.
     
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