Disc swap in progress

Discussion in 'Pre-1975 Build-Up/Project Threads' started by THorn, Apr 10, 2021.

  1. THorn

    THorn Member

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    1974 Hilux
    Aha, I’ve searched several recyclers, and I found a listing for a proportion valve for a 78 truck locally. I wonder why it’s not mentioned in parts catalogs? Maybe they don’t need replacement much? On further research, I did find a catalog that listed a discontinued prop valve for the RN30 trucks. It says ‘load sensor’, which might be hard to implement on this truck that wasn’t designed for it, but I’m thinking of giving this recycled one a try, to see if it makes this perform differently than my jegs valve.
     
    Last edited: Apr 16, 2021
  2. THorn

    THorn Member

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    Anyone have a photo of the RN20 valve? It would help me search.
     
  3. jetas

    jetas Grand Toyotaholic

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    Avoid anything like a LSPV
     
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  4. carinaguy

    carinaguy Member

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    You won't find one because it doesn't have one. The proportioning is built into the master. What most people assume to be a proportioning valve is actually just a distribution block. Like I said before, a prop valve is just an unnecessary complication for you at the moment.

    I did some research and ate some humble pie. Toyota didn't switch to a single piston caliper until '84, probably to go to a vented rotor. Anyway, it sounds like your system is balanced, so that isn't the issue.

    To check your booster: with the engine off, repeatedly press the brake pedal until all the vacuum is bled off. When the pedal won't get any firmer, press and hold down the pedal hard. If it slowly sinks any further, it is bad. I doubt this is your problem.

    Without knowing your bleeding procedure, it is possible to still have air in the master. I once replaced a master on my '73 Carina and had to bleed it 6 times. Then I learned about how to bench bleed and haven't had that experience since.

    Long story short, I now suspect your issue is in the master cylinder. Either an air bubble in the front brake circuit or a bad piston. The pedal should not go to the floor, so there is definitely an issue. I would want to get the master replaced before any warranty expires.
     
  5. THorn

    THorn Member

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    Thanks! That’s been my line of thinking too. The pedal is solid in the absence of the vacuum, which suggests that maybe I have some air trapped somewhere. I’m going to remove the master cylinder so that I can bleed it with different parts elevated. I did try to bleed it before I installed it, but being new to the process, I could well have been short of what was needed.
     
  6. carinaguy

    carinaguy Member

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    THorn,

    If you are interested in the steel rims from my '76, shoot me an email. carinaguy@yahoo.com

    I had been using them for rollers, but now the tires are completely shot and the rims are dead weight. If you want them they are yours. We just need to coordinate off the forum.
     
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