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cycling noise from PSE unit?

Discussion in 'Electrics, Vacuum, Ignition and ECU' started by gazbiker, Jul 13, 2019.

  1. gazbiker

    gazbiker New Member

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    Hi guys, i have recently bought a R230 SL350 2005 and getting to know the vehicle. Something i have noticed is a noise coming from the left hand sideof the boot the PSE unit i believe? It seems to be going through a cycling process? I have no warning lights and everything on the vehicle seems to work ok. Having done a bit of research i have established that the hydraulic resevoir is on the minimum mark but not below it, so not sure whether this would cause the PSE unit to be cycling? Am i imagining things, is this just normal or is something up? Any help appreciated. Cheers
     
  2. LostKiwi

    LostKiwi Senior Member

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    Ok. There are 2 pumps there.
    The one with hydraulic fluid is the roof pump. The PSE pump sits under it and uses air pressure/vacuum to provide central locking. Which one is it?
     
  3. OP
    gazbiker

    gazbiker New Member

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    The noise is coming from that unit, it is difficult to tell whether its the roof pump (hydraulic) or below the air vacuum as the unit is combined.
     
  4. LostKiwi

    LostKiwi Senior Member

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    No they are 2 separate pumps. The PSE pump is in a foam case mounted under the frame that supports the hydraulic pump.
    If the PSE pump gets wet (R230s are designed with water leaks) they can do weird things and will eventually fail (preventing access to the boot).
    It's most likely the PSE pump running and is most likely the result of a vacuum leak in one of the pipes. Allowing it to continue too long will burn out the pump sooner or later.
    Whilst you still have access to the boot make sure the metal key can unlock the boot. If the pump fails and it doesn't work you're in a world of pain.
    Also check for water in the boot floor and if at all in doubt remove the foam around the pump and dry it out.
     
  5. OP
    gazbiker

    gazbiker New Member

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    Hi lostkiwi

    Boot is dry: check, metal key still opens the boot: check

    Tomorrow i will try and establish which motor is running and go from there. The leaking vacuum sounds plausable so will listen out for leaks.

    I'll let you know how i get on.

    Do you think the hydraulic pump would be cycling if the oil level is just above minimum?

    Cheers

    Gaz
     
  6. LostKiwi

    LostKiwi Senior Member

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    I wouldn't have thought so. There wouldn't normally be a reason for the pump to run unless either the roof or roll bar were being operated.
     
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  7. OP
    gazbiker

    gazbiker New Member

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    Ok, i moved the hydraulic unit out of the way and established that it is definately the PSE unit that keeps on cycling. The unit itself looks clean, no damp and the pipes alllook in good order. I left the key in the ignition without the engine running and although the PSE unit was going like the clappers i could not hear any air leaks? It does seem to be effected by closing the drivers door though, i.e aalong as the drivers door is closed it stops? Is this normal for the PSE unit? Am i being oversensitive? I read somewhere that can put a vacuum guage on some where and charge the system and listen for leaks?

    Anyhelp ot guidance appreciated.
    Gaz
     
  8. LostKiwi

    LostKiwi Senior Member

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    The only way to check for leaks is to disconnect each line, apply a vacuum pump to it and make sure it holds vacuum. Did exactly that for a PSE issue on my r129 SL yesterday (and found no leaks).
     
  9. OP
    gazbiker

    gazbiker New Member

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    Hi Lostkiwi, I have managed to buy myself a vacuum tester for the PSE pipes. Presumably they clip out of the main body and you can connect the vacuum to each individual one and see whether the vacuum is being lost. What is the maximum vucuum that should be applied? I don't want to break a bellows? cheers Gaz
     
  10. LostKiwi

    LostKiwi Senior Member

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    450mbar is operating pressure/vacuum.
    Yes they just clip out. Be careful to pull straight so as not to break the retainer clips.
     
  11. OP
    gazbiker

    gazbiker New Member

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    Cheers for the info, going to atempt tbis on saturday.
     
  12. peterws1957

    peterws1957 Senior Member

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    I would think the most likely suspect will be the soft close unit in the boot lid. Made of cheap plastic they are prone to failure. Does the soft close work? If not take a look at MB World forum under the SL section - there's a good DIY guide for fixing.
     
  13. ajlsl600

    ajlsl600 Senior Member

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    or pipe under seat ? dislodged with seat fore aft movement ?
     

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