1. Registration trouble? Please use the "Contact Us" link at the bottom right corner of the page and your issue will be resolved.
    Dismiss Notice

Vacuum Brake Booster

Discussion in 'Early CJ5 and CJ6 Tech' started by mickeykelley, May 12, 2020.

  1. May 12, 2020
    mickeykelley

    mickeykelley Well-Known Member

    Republic of Texas
    Joined:
    Oct 10, 2015
    Messages:
    1,900
  2. May 12, 2020
    Fireball

    Fireball Well-Known Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Pullman, WA
    Joined:
    Feb 9, 2018
    Messages:
    5,622
    My dad has one on his V6 flatfender mounted under the hood on the right fenderwell. It took some extra plumbing, but it's been working well for 40 years.
     
  3. May 13, 2020
    BadGoat

    BadGoat How High Can You Climb?

    Northern Virginia
    Joined:
    Apr 27, 2017
    Messages:
    326
    I hadn't seen these before, so did some quick research. They seem to be an inline booster for a single circuit. So for the front brakes, you would run a single front brake line from the master cylinder, to the remote booster, then split the brakes somewhere between the remote booster and the individual front wheels. Looks pretty straight forward. I'd first make sure you have a dual circuit master cylinder setup on the frame rail, then plan on running all new front brake lines and plumb the remote booster somewhere you can get to it and avoid anything that would cause vacuum leaks, like the exhaust.

    There's some good info on them from the MG guys.

    Remote Brake Servo


    These instructions show them being used on a single circuit system to feed both front and rear brakes, but I wouldn't want to add another potential failure point on a single circuit brake system.

    https://mossmotors.com/media/instructions/981-173.pdf

    Here's another model.
    Master Power Brakes

    Mike
     
    Last edited: May 13, 2020
  4. May 13, 2020
    Oldriginal86

    Oldriginal86 Member

    Pasadena, Md.
    Joined:
    Nov 5, 2014
    Messages:
    589
    I installed one in mine years ago. Works but with the 9” brakes and big tires there only so much friction surface. I upgraded front brakes to 11” drums last year and made a substantial improvement. One issue with this booster is it only works with single circuit system, or put two boosters.
     
  5. May 13, 2020
    mike starck

    mike starck Member

    salem,oregon
    Joined:
    Jun 22, 2006
    Messages:
    762
    These have been around since the 1950's and as mentioned work on single circuit systems.GM had one they called "hydra-vac unit" I had that version on my '47 flattie.Worked great. I see used ones at swap meets.
     
  6. May 13, 2020
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
    Joined:
    Aug 10, 2003
    Messages:
    23,596
    Yep, I'd think their main problem is that they are a single circuit. I expect there's no reason you could not make the slave MC a dual system, and with some engineering I think you could design an all-dual system. Other than the MC going soft, there are plenty of failures of the wheel circuits a dual slave system would save you from. BTDT- the rear cross-axle tube on my J10 burst in the Home Depot parking lot. Brakes still worked sort-of.
     
  7. May 13, 2020
    colojeepguy

    colojeepguy Colorado Springs

    At the foot of...
    Joined:
    Apr 4, 2010
    Messages:
    7,110
    I would love to have one of those for a dual MC system.
     
  8. May 13, 2020
    Dne007

    Dne007 Well-Known Member 2024 Sponsor 2023 Sponsor

    Cypress, Tx
    Joined:
    Sep 2, 2019
    Messages:
    1,549
    Hi, I put that booster on my brothers '62 Willys(bought it for him for his birthday), Bought it from Kaiserwillys, but they're available from other venders. It goes for about 399, but I got 20% cause a asked;) Boy, I got screwed if Amazons price is only 100bucks!

    Overall, I'm not impressed, but that may not be fair as my brother has fairly large tires, with stock 9" brakes. I guess I was expecting it to feel it more.
    It has to be used with the stock master single cylinder; I put a remote lid with the remote reservoir on his.

    [​IMG]

    Thinking it wasn't getting enough vacuum, bought this auxillary vacuum pump (amazone) as its primary vacuum, may eventually incorporate engine vacuum plus this. It comes on after a few stops, runs for a few seconds. Not noticeable when driving, but when at a stop, it kind of vibrates ones feet a tiny bit.
    [​IMG]

    Robs jeep with my corral for a glamour shot;)
    [​IMG]



    On my current project, a '68, I went with Brennan Metcalfs disc brake conversionhttps://brennans-garage.com/products/trackick-disc-brake-conversion-bracket, I'm a way from getting to try it out, but I think I'd go with a better setup before buying the power booster in question and expecting extra ordinary results.
    [​IMG]

    I've long since had this installed and the brakes bled. The pedal is high and very firm;) I think it's going to be good;)
    [​IMG]
     
  9. May 13, 2020
    Fireball

    Fireball Well-Known Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Pullman, WA
    Joined:
    Feb 9, 2018
    Messages:
    5,622
    You can just run one booster for each circuit. There are some bundled back-to-back for nicer packging, but it's basically an independent servo for each brake circuit.

    Pricey one here: Master Power Brakes

    Cheaper from England, but not sure what the shipping costs: Medium Dual Circuit Remote Vacuum Brake Servo from Car Builder
     
  10. May 13, 2020
    Fireball

    Fireball Well-Known Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Pullman, WA
    Joined:
    Feb 9, 2018
    Messages:
    5,622
    Having had nearly useless boosted 9" brakes on my CJ-2, I think the brakes are a bigger problem than the booster.
     
    Dne007 likes this.
  11. May 13, 2020
    Howard Eisenhauer

    Howard Eisenhauer Administrator Staff Member

    Tantallon, Nova...
    Joined:
    Nov 22, 2003
    Messages:
    8,102
    Bendix used to (maybestill does) make them- basicly two units bolted back to back.

    Old School-

    [​IMG]
     
  12. May 13, 2020
    colojeepguy

    colojeepguy Colorado Springs

    At the foot of...
    Joined:
    Apr 4, 2010
    Messages:
    7,110
    Do these run on engine vacuum like a normal booster?
     
  13. May 13, 2020
    Howard Eisenhauer

    Howard Eisenhauer Administrator Staff Member

    Tantallon, Nova...
    Joined:
    Nov 22, 2003
    Messages:
    8,102
    Yes to the engine vac.
     
  14. May 13, 2020
    Dne007

    Dne007 Well-Known Member 2024 Sponsor 2023 Sponsor

    Cypress, Tx
    Joined:
    Sep 2, 2019
    Messages:
    1,549
    The system I bought came with an auxillary vacuum canister, it has like a 1/8 hose, and take a lot of plumbing to get it in line. I didn't use it. On the F-134 freshly overhauled engine, I thought I'd be a smarty and connect vacuum to the line at the PCV valve as it wasn't connected, the pcv was connected but there was a fitting which may have gone to some thing else, but vacuum at that point was only 12-16, and at the base of the carburetor was the same, but the 90 degree fitting which leads to the pcv, closest to the "intake" was 22-26 which would have worked, and I'd still may connect that line in addition to the auxillary vacuum pump. The reserve on the item in question is relatively small and good for only a few quick stops, then power brakes start to fade and back to "normal" braking. A large reservoir would be greatly helpful.
     
  15. May 13, 2020
    Howard Eisenhauer

    Howard Eisenhauer Administrator Staff Member

    Tantallon, Nova...
    Joined:
    Nov 22, 2003
    Messages:
    8,102
    Old photos of the Bendix hydrovac installs on F4's show a fairly large diameter vac hose going the the fitting under the carb. 1/8" seem *way* too small for a quick recharge.
     
  16. May 13, 2020
    colojeepguy

    colojeepguy Colorado Springs

    At the foot of...
    Joined:
    Apr 4, 2010
    Messages:
    7,110
    Normal vacuum boosters have 11/32 or 3/8 hose running to them, i would presume this needs something like that.
     
New Posts