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Thread: Brake servo push rod length??

  1. #1

    Brake servo push rod length??

    Hi All,

    I have a really strange issue I can't figure out for the life of me. I've been very slowly rebuilding my 95 VR over the last couple of years. I refitted the brake servo and master cylinder some moths back then today I bled the system with a power bleeder and all seemed well until I went to put the pin back in between the brake pedal and servo push rod.
    On reattachment is seems that the push rod is not long enough any more. When all the way out, the pedal is still depressed enough to be a few mm away from the brake light switch. I have tried pulling the rod out further but it's definitely no going to move any more. I know for certain that it has not been adjusted and is exactly how it was when I removed it. I then pulled it all back out again and looking inside it everything looks like it should. I really cannot understand what has happened. Could I have damaged it somehow when re-fitting it? Even if I had I can't see how it would cause this issue. Any thoughts or opinions would be much appreciated before I bite the bullet and buy a new servo.

  2. #2
    Had a feeling that one may draw a blank...! Any chance one of you kind folk might take a close up picture of how far the fork is screwed onto the end of the servo push rod?

  3. #3
    ⋆⋆ CF Member ⋆⋆
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    Around 130mm to the centre of the clevis pin hole on my spare

  4. #4
    Many thanks, that's a great help. It does look fractionally longer than mine, I'll have a measure later. Could you tell me how far yours is screwed on? On mine the end of push rod is about flush with the hole in the cross piece of the fork it would exit from if screwed in further. If yours is the same I'm guessing I've damaged the servo somehow.

    Cheers!

  5. #5
    Super Moderator Yandards's Avatar
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    Quote Originally Posted by Red Baron View Post
    Many thanks, that's a great help. It does look fractionally longer than mine, I'll have a measure later. Could you tell me how far yours is screwed on? On mine the end of push rod is about flush with the hole in the cross piece of the fork it would exit from if screwed in further. If yours is the same I'm guessing I've damaged the servo somehow.

    Cheers!
    You adjust the linkage length so the pin fits freely to get it to fit - its not an issue to do this as with the pedal in the spring loaded return position it is 'at rest'.

    As the brake servo is in contact with the plunger on the master cylinder then you are simply setting the rod position to the pedal resting position.

    So there is no issue with either your brake master cylinder or the servo.
    Cheers fool,
    Yan
    1990 G60-16v Blue Pearl Effect
    Now sold, 1991 Nugget G60
    CCGB Technical Secretary


  6. #6
    Hi Yandards, thanks for the advice. The reason I ask is after refitting the servo the pin no longer fits unless then brake pedal is too low - already 3-4 mm away from the brake light switch, which is odd as I haven't touched it since I removed it a year ago. The only thing I can think of is either someones fiddled with it whilst it was sitting in the garage or I bust something putting it back in, which was a bit of a wrestling match but seemed to go ok.

  7. #7
    Many thanks for your help on this guys. I measured my servo and it came up about 3/4 of a cm shorter than Dox's measurement. The lock nut was very tight so I'm not sure how on earth this has happened. Still a little concerned the servo is damaged, I'm going to fit it without the master cylinder then pump the pedal a bit to see if it remains solid. Here's hoping, as I have no desire to remove/refit it again any time soon - Not much fun at all!

  8. #8
    ⋆⋆ CF Donator ⋆⋆ captainredeye's Avatar
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    How did you get on with this? I have removed the servo then refitted and bled the brakes and found the brake pedal kisses the pedal light sensor but needs another 5mm to switch off the break lights.

    Is it figure 19 that you have to adjust?
    http://www.oemepc.com/vw/part_single/catalog/vw/markt/RDW/modell/COR/year/1994/drive_standart/76/hg_ug/614/subcategory/116020/part_id/3688223/lang/e
    Last edited by captainredeye; 30th March 2019 at 6:04 PM.

  9. #9
    CF Nutter fendervg's Avatar
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    Is the brake light pedal switch not threaded, so you can adjust the length - or is it already all the way in?
    ____________
    fendervg

    93 Corrado VR6
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  10. #10
    ⋆⋆ CF Donator ⋆⋆ captainredeye's Avatar
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    i Didn’t notice but that is a good shout will have another look in the morning.

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