Results 1 to 22 of 22

Thread: Pilot brakes stay engaged

  1. #1

    Join Date
    Dec 2018
    Posts
    4
    Post Thanks / Like

    Pilot brakes stay engaged

    Good evening,

    Before I tear into a brake overhaul, curious what you think of this issue.

    1950 -18, Cleveland 30-60A double pucks, Scott 4200 parking brakes, North River Boosters.

    Co-pilot brakes work great. Piston pushes pedal aft when released.

    Pilot brakes engage and will not release...really noticeable when slow taxiing and needing plenty of power for small movements. Like having parking brake engaged all the time. I have to hook my heels behind pedals and pull them back to disengage.

    Is the linkage gummed up under the floorboards, or is that a sign of weak internals? No noticeable leaks.

    Thanks,
    Chris
    Likes windy liked this post

  2. #2
    aktango58's Avatar
    Join Date
    Aug 2004
    Location
    18AA
    Posts
    9,023
    Post Thanks / Like
    I am scratching my head, the pedals in front should have a cable or rod connecting them to the brake master under the seat. Is this your setup?

    There is some brackets holding the brake pedals to the floor boards, pull the panels from behind the boot cowl and you should be able to reach them and check things out.
    I don't know where you've been me lad, but I see you won first Prize!

  3. #3
    www.SkupTech.com mike mcs repair's Avatar
    Join Date
    Aug 2004
    Location
    chugiak AK
    Posts
    10,132
    Post Thanks / Like

    Pilot brakes stay engaged

    New install??

    Front pedals ARE NOT properly shimmed/free moving.

    Give us more information


    Sent from my iPhone using SuperCub.Org

  4. #4

    Join Date
    Dec 2018
    Posts
    4
    Post Thanks / Like
    I know, it is crazy. It has cables connecting front to rear brakes.

    When pilot brakes engage, the cable obviously pulls the rear pedals forward, but the piston is unable to return any of the pedals.

    When only rear brakes engaged, the piston snaps the rear brakes back just fine.

    I also pulled the inspection panels under the front brakes and everything looks good, but maybe needs cleaning and fresh lubrication??

  5. #5

    Join Date
    Dec 2018
    Posts
    4
    Post Thanks / Like
    No, opposite of a new install. This setup has been in the cub for many many years, but i don't have any good information on them except the symptoms I've noted.

    Everything in the brake system is fresh outside of the cabin. Everything in cabin is old. Fresh bleed job. Calipers move freely in torque plates prior to brake application. However, they remain tight and locked at first application of front brakes because they do not return aft.

    For example, I start my taxi and do a brake check. I have to physically pull brakes back. But...if I had a co-pilot in rear do the braking, the whole shebang would work perfectly.

  6. #6
    behindpropellers's Avatar
    Join Date
    Feb 2003
    Location
    NE Ohio
    Posts
    6,657
    Post Thanks / Like
    Tango cub with toe brakes?

  7. #7
    www.SkupTech.com mike mcs repair's Avatar
    Join Date
    Aug 2004
    Location
    chugiak AK
    Posts
    10,132
    Post Thanks / Like
    Let fluid out of brakes. Now go move front pedals. Are they free moving? I doubt it. Fix that. Then refill. Only thing that makes sense from you descriptions


    Sent from my iPhone using SuperCub.Org

  8. #8
    skywagon8a's Avatar
    Join Date
    Mar 2008
    Location
    SE Mass
    Posts
    8,987
    Post Thanks / Like
    Quote Originally Posted by mike mcs repair View Post
    Let fluid out of brakes. Now go move front pedals. Are they free moving? I doubt it. Fix that. Then refill. Only thing that makes sense from you descriptions
    Alternatively, disconnect the interconnect cable from the master cylinder pedal. This will isolate the front pedals. Now find what is binding the front pedals. Spring broken and binding? Clamps binding the pedal pivot under the floor? Those front pedals are supposed to have a spring which pulls them towards the release position. Pedal pivot tube worn and dragging under the floor?
    What ever you find by your description the entire trouble is with the pilots pedals. Nothing wrong with the brakes.
    N1PA
    Likes BC12D-4-85, bob turner, Hardtailjohn liked this post

  9. #9
    Steve Pierce's Avatar
    Join Date
    Mar 2002
    Location
    Graham, TX
    Posts
    18,357
    Post Thanks / Like
    Quote Originally Posted by skywagon8a View Post
    Alternatively, disconnect the interconnect cable from the master cylinder pedal. This will isolate the front pedals. Now find what is binding the front pedals. Spring broken and binding? Clamps binding the pedal pivot under the floor? Those front pedals are supposed to have a spring which pulls them towards the release position. Pedal pivot tube worn and dragging under the floor?
    What ever you find by your description the entire trouble is with the pilots pedals. Nothing wrong with the brakes.
    Ditto what Pete posted.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  10. #10
    Stew's Avatar
    Join Date
    Jul 2013
    Location
    Haywards Heath, UK
    Posts
    114
    Post Thanks / Like
    Couple of things.

    Just looking at the standard system, left and right brake are completely independent and there is no return spring on the front pedals, the rods/rear pedals/master cylinder internal coil springs pull them back.

    If both pedals are sticking in the forward "brakes on" position then they individually have the same problem and it is either binding/bent shafts or weak/broken springs in the master units.........probably.

    Kind regards

    Stew
    Likes DENNY liked this post

  11. #11
    skywagon8a's Avatar
    Join Date
    Mar 2008
    Location
    SE Mass
    Posts
    8,987
    Post Thanks / Like
    Quote Originally Posted by Stew View Post
    Couple of things.

    Just looking at the standard system, left and right brake are completely independent and there is no return spring on the front pedals, the rods/rear pedals/master cylinder internal coil springs pull them back.

    Stew
    You're right, I was thinking of the rudder pedal spring.
    This is what it looks like under the floor. There is something in that lower mechanism which is binding. Loosey goosey is best.


    It's not a fault of the master's springs. If it were they wouldn't be functional from the back seat. Also those springs are not strong enough to overcome a defect in the front pedals.
    N1PA
    Likes C_Bailey liked this post

  12. #12
    Steve Pierce's Avatar
    Join Date
    Mar 2002
    Location
    Graham, TX
    Posts
    18,357
    Post Thanks / Like
    I still think if you disconnect the interconnect you find your issue.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers
    Likes skywagon8a, MT12, Hardtailjohn liked this post

  13. #13

    Join Date
    Feb 2002
    Location
    don
    Posts
    666
    Post Thanks / Like
    Check park brake valve if it has one. Mine locked on landing. Ugly!

  14. #14
    skywagon8a's Avatar
    Join Date
    Mar 2008
    Location
    SE Mass
    Posts
    8,987
    Post Thanks / Like
    Quote Originally Posted by don d View Post
    Check park brake valve if it has one. Mine locked on landing. Ugly!
    That can cause issues, but does not match the description of Chris's trouble.
    N1PA

  15. #15
    www.SkupTech.com mike mcs repair's Avatar
    Join Date
    Aug 2004
    Location
    chugiak AK
    Posts
    10,132
    Post Thanks / Like
    Rereading this and ignoring your info.... see if brakes are free in calipers and if pistons are freely moving


    Sent from my iPhone using SuperCub.Org

  16. #16

    Join Date
    Sep 2003
    Posts
    6,579
    Post Thanks / Like
    It is the front pedals. Either shoot some Tri-flow in there with cables released, or go in there and put shims between the U brackets and the frame brackets.

    The parking brakes have nothing to do with this, but can be serious problems themselves. They get inadvertently applied, often at the wrong time.
    Likes Hardtailjohn liked this post

  17. #17

    Join Date
    Dec 2018
    Posts
    4
    Post Thanks / Like
    Thank you everybody. Won't be able to dive into it until Friday morning. I hear all suggestions, but am very certain as Bob mentioned that working something like tri-flow into the pedals and/or shimming will end up being solution. Not certain how difficult it is to access the lube and/or shim job as I just moved from a cessna to this cub. The circular inspection panels under the pedals don't seem to fit much more than a flashlight..

  18. #18
    algonquin's Avatar
    Join Date
    Apr 2013
    Location
    Seldovia,Ak
    Posts
    823
    Post Thanks / Like
    For your first time working on Cub brakes why not find a A&P that will work with you on this and then you will know how things are set up. If the brakes lock up on landing a Cub will go on its nose costing a whole bunch more than an hour with a mechanic.Most guys will work with you thru this, also most don't even bite ( to hard) good luck with it.

  19. #19
    Stew's Avatar
    Join Date
    Jul 2013
    Location
    Haywards Heath, UK
    Posts
    114
    Post Thanks / Like
    Hope you get to the bottom of it on Friday, another pair of hands would really help as it is easier with someone on top with a spanner when you loosen the nuts on the pedal shaft saddle underneath, 1/4" drive socket set is good too.

    Disconnecting the pedal interconnect is excellent advice but if the pedal interconnect is a rod, that is a bit of a struggle to disconnect unless you have to. Before you embark on that, get your helper to apply full brake on the back/main pedal and then move the front pedal with your hand bending the rod a little, you might confirm where the problem is without disconnecting.

    Slightly concerned that the problem is both sides when the left and right brakes are completely independent. The only common part is the fitter who intalled them and they possibly did not shim them correctly and the shafts are tight in the saddle.

    Here is a diagram of the system, pm me with an email and I will send you the original so you have a clearer copy.

    Kind regards

    Stew

    13399_Brake Installation.jpg

  20. #20
    skywagon8a's Avatar
    Join Date
    Mar 2008
    Location
    SE Mass
    Posts
    8,987
    Post Thanks / Like
    Quote Originally Posted by Stew View Post
    Note on this drawing the interconnect is swaged at both ends. If yours is like this you can remove the AN-3 bolt (sometimes this is a clevis pin) which holds the pedal to the master cylinder. This will release any connection between front and back without disturbing the master cylinder.
    N1PA
    Thanks Travelair3000 thanked for this post
    Likes bob turner, Hardtailjohn liked this post

  21. #21

    Join Date
    Sep 2003
    Posts
    6,579
    Post Thanks / Like
    Or, simpler, just get a block of wood, and apply the rear brake with it wedged against something - the rear seat pan, maybe. Then work that front pedal until loose.

    We kinda like the aftermarket rods, which approximate the original welding rods only with clevises and AN-3s holding the ends to the pedals. Makes adjustment trivial! Doesn't weigh much more than cables with swages.

  22. #22

    Join Date
    Apr 2018
    Location
    Knoxville, Tn.
    Posts
    151
    Post Thanks / Like
    I'm not a mechanic, but I slept in a Holiday Inn about 15 years ago when the Hampton Inn was full.

    If Triflow or WD-40 don't fix the problem, then disassemble and reassemble the pedal assemblies. My basic approach to everything broken since I was a kid - first WD-40, then if still broken, take it apart. I'm still alive after all these years.

Similar Threads

  1. I think I'm going to stay "Sport Pilot"
    By Richgj3 in forum Cafe Supercub
    Replies: 47
    Last Post: 08-08-2016, 11:44 AM
  2. Starter bendix stays engaged
    By Helmetfire in forum Super Cub Sick Bay
    Replies: 3
    Last Post: 05-20-2013, 11:14 PM
  3. Stay tuned....
    By StewartB in forum Cafe Supercub
    Replies: 7
    Last Post: 11-05-2003, 09:38 PM

Bookmarks

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •