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Thread: Need brake bleeding advice

Discuss the Austin Healey Sprite and the MG Midget. Two different but similar cars sometimes referred to collectively as the Spridget.

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    Need brake bleeding advice

    1975 Midget 1600 Installed new brake master cylinder as old one had an unfixable leak. Both my Midget shop manuals *did not*specify bench bleeding the new master, a chore I chose to avoid since I didn't need more brake fluid slopped around hooking up the brake lines to the master. Since this is a solo project I got out the MiteyVac and tried to draw some new fluid from the filled-up master via front wheel bleed screw. It won't draw any significant fluid whether brake pedal is depressed or not. 30psi on the gauge.

    Going to the other front wheel, I got a positive indication and the level in the master went down a little. Can't hook up line to rear wheels as the bleeder screw is too close to the brake drum edge to accommodate the vac line and wrench.

    Cannot get any pedal at all. By the way, tried bleeding air out of master by loosening brake line connections with pedal depressed...can't tell if it worked. Seems like maybe one side of master is working and other is not. Didn't check closely on respective reservoir levels. I've done the brakes and clutch on this car several time before but I'm stumped.

    TIA for any suggestions that you may provide while I go back out to cuss at the car some more. Jim

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    Luke Skywalker
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    Re: Need brake bleeding advice

    You need to adjust the rear brake shoes...if you have front shoes do the same.
    Start bleeding at the cylinder the most away from the master and follow until you finish at the closest.
    Be sure to check the level on each cylinder.
    I finish up with a person doing the pedal. Don’t agitate the fluid.
    Cheers,
    D.
    "If it's got t*ts or tyres, you've got problems"
    www.englishmotorsatfairbrook.org
    TVR Car Club North America Southwest Regional Organiser

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    Great Pumpkin JPSmit's Avatar
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    Re: Need brake bleeding advice

    Before you go too far down the road of frustration pull and clean your 'splitter' - I was stunned how much crap there was. Also, while you are doing this have you changed your rubber hoses? If not this would be a great time!

    splitter.JPG
    John-Peter Smit
    1976 MG Midget
    1969 Vauxhall Viva GT
    1958 Fiat Multipla (Barn art)

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    Yoda dklawson's Avatar
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    Re: Need brake bleeding advice

    Your first post suggests that you have owned and driven the car for a while. If that is not true please let us know. I apologize in advance if any of the information below is obvious or redundant to what you know and do.

    As mentioned above, adjust the rear brakes first. Lock them with the adjusters then back the adjusters off so you can turn the wheel and hear a bit of scraping of the shoes on the drums. You do not want the adjusters so loose that there is no drag.

    The "splitter" mentioned above is the PDWA (pressure differential warning assembly). If it is full of crud it can block the distribution of fluid. Cleaning may help. There are a couple of different PDWA designs used on British cars and replacement seals are not available for all of them. I would not touch the PDWA until you have tried a couple of other things first.

    The flexible rubber brake hoses at each wheel will collapse internally when old. They will look fine on the outside but when collapsed inside they effectively block (or trap) brake fluid. If your car's brake hoses are old and rubber it is a good idea to replace them before proceeding with bleeding. Some people (myself included) replace the flex lines with the Teflon hoses covered with metal braid. Unlike the rubber hoses the braided ones last indefinitely.

    I know you want to avoid more mess with spilled fluid but I still suggest you try the following.
    Top up the MC reservoir.
    Make sure all the brake fittings are tight (both sides, front to back).
    Start at the master cylinder. Place paper towels around/underneath its fittings. Loosen the fittings about 1/2 to 3/4 turns.
    SLOWLY press the pedal down while you have an assistant watch for fluid leaking around the fittings.
    When your helper sees fluid at the loose fittings, hold the pedal where it is and have your helper tighten the fittings.
    Now release the pedal and move down each brake line from the MC repeating the process (open fitting, pump to leak, then re-tighten).

    Once you have done that front to back on both sides, proceed to whatever method you like for bleeding brakes. Everyone has their preference and I am not about to tell you that the method I like is right or better. However, I will mention that with vacuum bleeders as you mentioned it is often beneficial to put some form of sealant on the bleed nipple threads. The threads are on the dry side of the brake system so you can use just about any thread sealant you want. I have used Teflon tape and I have used silicone grease depending on which was available at the moment.

    With the system bled you should have a pedal. If you are using DOT-5 fluid it is very easy to get tiny bubbles in the reservoir and lines during the filling and bleeding process. With DOT-5 you may need to bleed a second time after allowing things to sit overnight.

    Assuming you have a pedal, you MAY see the PDWA dashboard warning light is on. If that happens, post back for information on how to center the PDWA spool so the warning light turns off.
    Doug L.
    '64 Morris Mini Cooper-S 1275
    '67 Triumph GT6 Mk1

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    Re: Need brake bleeding advice

    Thanks to all for your suggestions. After repeated bleeding I now have a nice pedal and no visible leaks. Post-maintenance drive incident-free. Took patient petal pusher out to dinner. I had been completely through this brake system a few hundred miles ago but this car always finds a way to flummox me. Jim

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    Re: Need brake bleeding advice

    Yes, they are like that.
    Was Man nicht im Kopf hat muss Man in den Beinen haben
    '48 Ford Prefect
    '67 Sprite (project)
    '74 Super Beetle
    http://enfoprefect.org

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    Re: Need brake bleeding advice

    With older cars a complete change of fluid is sometimes needed. If the fluid I’d DOT3 it should be clear and light.
    I had a power flush done on another car (95 Jag XJS) I bought. Both the brake fluid and the PS fluid were black and nasty. Cost $125 for power flush. Money well spent.

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