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Residual valve problem?

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  • Brakes: Residual valve problem?

    I installed a dual master cylinder on my 1964 Avanti while I was also adding modern style disc brakes. After hitting the brakes the calipers are locking up. First I suspected that I did not adjust the rod going into the master cylinder to the correct length but double checked it and it is fine. I can also tell that is not the problem since I can take the master cylinder off of the power booster and they are still locked up. If I crack the front brake line where it goes in the master cylinder the rotors turn fine. I used the master cylinder that is called out on Bob Johnstone's site that is supposed to fit Chrysler A, B, and C body cars 1967 to 1970 with drum brakes (NAPA part #ts101323). When I look up residual valve info on the internet it told me that a drum brake system residual valve will not work properly on a disc brake conversion. Does anyone know if that type of master cylinder does use a residual valve and if so can I remove them as shown on Bob Johnstone's site? I do like this type of master cylinder since it has a bolted down cap on it instead of the spring loaded wire clip type and is low profile so it clears the hood.

  • #2
    Do you have the front chamber of the master going to the rear brakes?
    Sometimes you can remover the residual check valve from the master, and then add the proper psi valve inline (but the proper master would be better).
    Drum brake residual valves are 10psi and disc valves are 2 psi.

    Originally posted by PACKERBACKER View Post
    I installed a dual master cylinder on my 1964 Avanti while I was also adding modern style disc brakes. After hitting the brakes the calipers are locking up. First I suspected that I did not adjust the rod going into the master cylinder to the correct length but double checked it and it is fine. I can also tell that is not the problem since I can take the master cylinder off of the power booster and they are still locked up. If I crack the front brake line where it goes in the master cylinder the rotors turn fine. I used the master cylinder that is called out on Bob Johnstone's site that is supposed to fit Chrysler A, B, and C body cars 1967 to 1970 with drum brakes (NAPA part #ts101323). When I look up residual valve info on the internet it told me that a drum brake system residual valve will not work properly on a disc brake conversion. Does anyone know if that type of master cylinder does use a residual valve and if so can I remove them as shown on Bob Johnstone's site? I do like this type of master cylinder since it has a bolted down cap on it instead of the spring loaded wire clip type and is low profile so it clears the hood.
    HTIH (Hope The Info Helps)

    Jeff


    Get your facts first, and then you can distort them as much as you please. Mark Twain



    Note: SDC# 070190 (and earlier...)

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    • #3
      On an Avanti there is no need for a residual check valve.
      Yes, I know the rear brakes are drums, but Bendix designed them for use without a check valve, while every other drum brakes I know of needs a 10 lb check.
      The 2 lb check valves are only needed if the master cylinder is under the floor.
      Last edited by mausersmth; 05-26-2011, 08:08 PM. Reason: aye kant spel!

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      • #4
        To set the record straight, that master cylinder does have residual valves. I took them out and now the calipers are not locked up. The only drawback that I can see in using that master cylinder is that the reservoirs are on the small side to be used on a car with disc brakes.

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