leaky rear cylinders on the D
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  1. #1
    Join Date
    Sep 2014
    adelaide hills

    Default leaky rear cylinders on the D

    I thought I had done well to replace the cylinder seals and boot on the rear to fix a leak however when I decided to take another look I noticed a couple of tablespoons worth of oil sitting in the boot. I realize it will still get returned back via that thin tube on the top but don't know how much blowby is acceptable?.
    What are people thoughts?


  2. #2
    Real cars have hydraulics DoubleChevron's Avatar
    Join Date
    May 2000


    It leaks by design. If it's dripping onto the ground. You will need to replace the rear boots. They will be split where you can't see the hole!

    The leakage would have to be huge to cause and issue ... the pump cycle time would probably only be a few seconds to.

    Shane L.
    'Cit' homepage:
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  3. #3
    Fellow Frogger!
    Join Date
    Nov 2010


    Hi Shane,

    Actually, no, they were not designed to 'leak by design' . Early cars that just used rubber rings for the cylinder seals had no leakage in the rears until the seals wore out. Though when they went the leakage was fairly substantial (as was also the case in the front). When the factory changed the seal design (Teflon sealing ring and a rubber compression ring behind it) the longevity factor went way up. The problem with the design is that Teflon does not seal well in low pressure applications. And the pressure in the rear of a D sedan is right on that 'pressure edge' if you will. A Break uses the same sealing system and the rear does not seep nearly as much as sedan - slightly more pressure in the spheres. The fronts of both cars remain, basically, dry until the Teflon seal really wears out. Again one is dealing with a lot more pressure.

    The other factor that makes the LHM cars leak more (exterior leakage) than LHS cars (ones using the same exact sealing system) is caused by the boot material. Those boot, being exposed to the elements, and being made out of Nitrile rubber is not nearly as 'weather' resistant as the EPDM rubber based boots of the LHS cars. The result is that the LHM units are far more prone to failure at the 'inversion' point compared to the LHS ones. In the US we really saw this as we were stuck with the LHS cars until February (IIRC) of 1970 (1969.5 of the model year)


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