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Thread: 70 240z maste cylinder problems

  1. #1
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    Jul 2014
    West Grove, PA

    Default 70 240z maste cylinder problems

    Hello All,
    First off i am new to my Z, and new to the forum. Im sure my problem has been discussed previously but i am having some very odd symptoms! I bought my car maybe 2 months ago. After sitting 30 years in dry storage the whole brake system was shot. I purchased all new pads and shoes and retainers and rebuilt the calipers and the wheel cylinders, along with new flex lines. I also bought the correct master cylinder for my car, it being built in 12/1970. My problem is that even after bleeding the entire system, i cannot get pressure to the front calipers. The bleeder on the master to the rear has pressure, but the front bleeder, once opened, does not. The pedal pumps up and seems rock hard. Please I have no idea why i am not getting pressure to the front system. Oh and the reaction disk is glued to the back of the pushrod so that did not fall out of place.

  2. #2
    Registered User EuroDat's Avatar
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    Feb 2012
    The Netherlands


    Welcome to the club.
    Reading your description of the problem Im wondering if your master cylinder is assembled correctly.
    I have read threads on this forum and other forums where people have found the internals fitted backwards or in the wrong order. Nothing missing, just a question of poor quality control at the factory. An example could be the primary cup on the front piston is fitted backwards.
    I take it you rebuilt the calipers per FSM instructions, but the MC was new and you probably fitted it without dismantling it.

    You mention that you bled the brakes. How did you do that? Im wondering how it bled seeing it doesn't build up any pressure when you pump the brakes. Maybe a vacuum bleeder?

    Did you check the adjustment on the rod from the booster? It could be pushing to far out and not allowing the pistons to return and open the resivoir holes. Vacuum bleeding can still bleed it like this, but not completly. There will be air trapped in the mc.

    Another probable cause is a huge amount of air in the front system, but then you wouldn't get any peddle hight. This can be caused by fitting the calipers to the wrong side. Check the bleeder is at the top of the caliper. Its an easy mistake to make because it all bolts up perfectly.

    5/77 280Z HLS30 403100 with some modifications
    Original colour: 305 Light Blue. The PO changed it to Red

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