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Thread: 1978 R100RS bleeding rear brake difficulty

  1. #1

    1978 R100RS bleeding rear brake difficulty

    Hi all,
    Rebuilt my rear master cylinder and installed new Speigler lines front and back and speed bleeders al around. Bled the front with no problem at all. Have just been trying to bleed the rear for well over an hour. No luck and what seems like an endless supply of air. All connections are tight. Any clues? Thanks

  2. #2
    Liaison 20774's Avatar
    Join Date
    Sep 2005
    San Antonio, TX
    I've never had to do a rear caliper but what I remember reading is that you'll probably have to take the caliper off its mounts and reorient it so that the bleed valve is at the highest spot. Probably will need to put a thin piece of wood between the pads to simulate the disk.
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  3. #3
    Like the front master cylinder, the rear one has a very small hole in it. If this hole is plugged fluid will not be drawn from the reservoir on bleed. The problem is, on the rear master cylinder the only way to access the smaller hole is to remove the plastic fitting on top that the feed hose to the remote reservoir connects to. This can be a task as it is a difficult press fit into a shaped rubber seal. Replacement fittings and seals are available from Brembo.

    Kurt is correct on the orientation of the caliper itself when bleeding.

    Good luck with the repair.
    -Live as fully as you can as long as you can-

  4. #4
    Registered User TEDZEMLICKA's Avatar
    Join Date
    Aug 2006
    Southeast Iowa
    I'm doing the same on a 1984 with similar results.

  5. #5
    -Live as fully as you can as long as you can-

  6. #6
    Thanks for all of the good advise. I pulled the master cylinder off and as you suggested pulled the spigot and grommet and found that one of the two small holes was plugged with black sludge. It was the hole closest to the operating arm. Now need to check with Steve at Bevelheaven to try and find a new spigot/ grommet

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