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Thread: Brake Servo failure, Marina based Roadster

  1. #1 Brake Servo failure, Marina based Roadster 
    club member Club Member wolf_rueffel's Avatar
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    Hello,


    unfortunately i have a problem with the servo brake on my Marina based Roadster.
    No pressure builds up. It seems like the servo is leaking
    The master cylinder is fine and everything is made new.
    As soon as I disconnect the vacuum hose, I can brake. And the engine runs smoother ... :-(

    You can also hear a whistle when I press the pedal and the pedal falls forward ... Pffft ..

    Is it possible to repair anything on the servo at all? Or does it have to be new?
    I saw that one screw from the servo is covered by the chassis, I hope I don't have to remove the entire unit:
    Clutch pedal, Gas pedal, and brake pedal?

    Do you have a tip for me?
    And maybe also a tip for a servo replacement, if necassary ?

    I thank you for your help

    Regards
    André

    IMG_3735s.JPG
    IMG_3734s.JPG
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  2. #2 Re: Brake Servo failure, Marina based Roadster 
    club member Club Member wolf_rueffel's Avatar
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  3. #3 Re: Brake Servo failure, Marina based Roadster 
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    There are companies that can repair servos - however it can be expensive. I am rebuilding a Marlin at the moment and have used a TR6 servo which fits and are available new. My car is far from being completed so can't tell you how well it works!
    Cheers Robin
    PS some pictures in my build thread.
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  4. #4 Re: Brake Servo failure, Marina based Roadster 
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    Hi Andre

    From your photos it's not clear how you managed to run the car to establish this problem, as there is no cylinder head fitted to the car?

    1) In the first instance , the rubber where the vacuum fitting fits into the servo doesn't look great, are you sure that it doesn't have a split in it ?
    2) Was the rubber hose going from the servo to the inlet manifold and their 2 clamps tight and in good condition?

    3) I would also check the underside of the servo from beneath the car looking upwards , as they do corrode on the bottom and there is a chance it's rusted through.
    Last edited by Ye Ol Ripper; 24-08-2021 at 09:40 AM.
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  5. #5 Re: Brake Servo failure, Marina based Roadster 
    club member Club Member wolf_rueffel's Avatar
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    Hello Robin,

    looks like mine...
    f you haven't installed it yet, you can give me the dimensions of the distance to each other
    for the fastening screws. Also for the brake cylinder fastening Sc. there is an old Lockheed installed on mine...
    Thats would be helpfull,
    And do you have a spare part number?


    Thanks for help !

    André
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  6. #6 Re: Brake Servo failure, Marina based Roadster 
    club member Club Member wolf_rueffel's Avatar
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    Hi Does the engine run better with the lid on? Then I want to try it :-)

    I'm not sure if the white connection nipple is ok ... There is probably a replacement ...
    The vacuum hose is OK, If I try to pull vacuum with my mouth, it doesn't stay, no chance ... :-(

    It is definitely not rusted, Dave Cunnington revised the Marlin some time ago, there is also a report here ...
    Therefore the pictures are also without Cylinder head ...
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  7. #7 Re: Brake Servo failure, Marina based Roadster 
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    Hi Andre
    Thanks for the clarification ,I now recall your car and also your you tube footage when you first got it .

    With the engine running and servo hose attached the easiest way to determine where an air leak is as follows:

    Using Carb cleaner or WD40 spray using the straw around the servo fittings and if its sucking in air at the place you are spraying, the engine note/speed will change.

    If the fittings seem fine then repeat around the servo to try and locate a perforated hole.

    I also recommend removing the white elbow fitting, remove the rubber grommet , sand off the corrosion from the servo where the grommet contacts . The white elbow fitting should be a very tight fit when pushed into the grommet to make an air tight seal.

    Are there any cracks in the White Elbow?

    Both the elbow and rubber seal were probably used on other British cars

    Possibly MGB and Triumph Dolomite's used the same servo seal and elbow.
    Last edited by Ye Ol Ripper; 24-08-2021 at 09:56 AM.
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  8. #8 Re: Brake Servo failure, Marina based Roadster 
    club member Club Member wolf_rueffel's Avatar
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    Quote Originally Posted by Ye Ol Ripper View Post
    Hi Andre
    Thanks for the clarification ,I now recall your car and also your you tube footage when you first got it .

    With the engine running and servo hose attached the easiest way to determine where an air leak is as follows:

    Using Carb cleaner or WD40 spray using the straw around the servo fittings and if its sucking in air at the place you are spraying, the engine note/speed will change.

    If the fittings seem fine then repeat around the servo to try and locate a perforated hole.

    I also recommend removing the white elbow fitting, remove the rubber grommet , sand off the corrosion from the servo where the grommet contacts . The white elbow fitting should be a very tight fit when pushed into the grommet to make an air tight seal.

    Are there any cracks in the White Elbow?

    Both the elbow and rubber seal were probably used on other British cars

    Possibly MGB and Triumph Dolomite's used the same servo seal and elbow.

    Thank you for the great tips. That's exactly how I'll do it ..
    And I will report.
    The "White Elbow" doesn't look very trustworthy, maybe that's my problem?
    I have a start pilot, so I will search for the hole against ...

    André
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  9. #9 Re: Brake Servo failure, Marina based Roadster 
    club member Club Member stevejgreen's Avatar
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    The white elbow is a non return valve. Part number RTC812P available from Rimmer Brothers


    edit, corrected part number
    Last edited by stevejgreen; 27-08-2021 at 09:48 AM.
    MOC member since 05/97
    1984 Marlin Roadster SWB.
    1800TC, Unleaded ported head, stage 2 cam. Ford Type 9 gearbox, Dolomite Sprint rear axle fitted with MGF disc brakes.
    Three core radiator, Renault Clio vented front discs.
    The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.

    Loads of Marlin Reference can be found documents here or there.
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  10. #10 Re: Brake Servo failure, Marina based Roadster 
    club member Club Member wolf_rueffel's Avatar
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    Hello !

    Yesterday I tried your tips ...
    Unfortunately, it's not the "elbow" valve.
    It works fine and is tight. Everything around the brake servo is also sealed.
    The "PFFFT" sound comes from inside :-( So the brake servo has to be removed after all :-(

    Probably the diaphragm is defective !? Then it will be a little more work ...

    Maybe Robin (Martinclan56) can give me the part number of his brake booster?
    This would be helpful

    Thank at all!

    André
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