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Technical Mustang II Brakes will not stop OK keyboard Mechanics your time to shine

Discussion in 'The Hokey Ass Message Board' started by hotrodhomework, Aug 21, 2019.

  1. hotrodhomework
    Joined: Aug 23, 2006
    Posts: 99

    hotrodhomework
    Member

    Update we are waiting on a Electric vacuum pump. The up28 is on its way from the great Amazon. I’ll talk my friend into ordering the vacuum pump 14 inches of vacuum is just not enough
     
    6-bangertim likes this.
  2. wandi harry
    Joined: Jul 19, 2008
    Posts: 239

    wandi harry
    Member

    getting a good firm pedal is what is needed before I would worry about the composition of brake pads.
    Have you tried isolating the front or rear system ? might give a bit of an idea if one system is the problem one
     
    s55mercury66 likes this.
  3. hotrodhomework
    Joined: Aug 23, 2006
    Posts: 99

    hotrodhomework
    Member

    I have not but I have remove both lines from the master cly and in installing plugs in the master cly test the master cly to see if we could pump pressure against the plugs it would not . I rebled the master and found very small amount of air in the master but after the test but did not test it with the plugs installed. Then we bled the whole system again. Nothing changed. I am going clamp of they rear line ( it the only rubber one in the system) and drive it to see. I am tied of bleeding brakes.
    Me and him are going to give all this a rest. We got about 20 hours in this brake system and not any better.
     
  4. hotrodhomework
    Joined: Aug 23, 2006
    Posts: 99

    hotrodhomework
    Member

    I thought I found air this is going to fix it but that is not the case.
     
  5. I fail to understand when there is one of these threads why there is no logical diagnostic process, the master would not build pressure so let’s just bleed it and throw parts at the rest of the system. Plug the master see if it build pressure. Hook up one side of the system see if it builds pressure. Brake systems are not rocket science.


    Sent from my iPhone using H.A.M.B.
     
  6. David Gersic
    Joined: Feb 15, 2015
    Posts: 2,321

    David Gersic
    Member
    from DeKalb, IL

    If the master, plugged, won’t build pressure, stop there. You’ve got junk.

    If this thing has steering, there must be rubber lines to the fronts too. A coupler, a flare nut, and a short length of crimped tubing can be used to plug parts of the system to see where you’re losing pressure. A brake pressure gauge would be nice to have for this kind of thing.

    I once spent a couple of weeks on a similar problem, was buying brake fluid in bulk.



    Sent from my iPad using The H.A.M.B. mobile app
     
    Hnstray and gimpyshotrods like this.
  7. hotrodhomework
    Joined: Aug 23, 2006
    Posts: 99

    hotrodhomework
    Member

    I was making 900 psi at the calipers so the master was making pressure I would like see a 1000 or close to it. If you go to 1 bore master it increase it about 980 to 990(close to 1000) so I tried it but Pedal stroke was to long.
    I reinstall the first master(1 1/8 bore) that is where I got some air in the master. I applied a logical process not a throw parts at it process but I did not get the pressure at the rear rear wheel cly. But 900 psi at the front should stop a car. A friend has a truck with the same set up and has 900 ft and 650 at rear and it stops great.
     
  8. hotrodhomework
    Joined: Aug 23, 2006
    Posts: 99

    hotrodhomework
    Member

     
  9. hotrodhomework
    Joined: Aug 23, 2006
    Posts: 99

    hotrodhomework
    Member

    900 psi front Braided steel flex brake lines front and rubber rear. Can not clamp off the braided steel lines on the front will damage them but I can block off the rear rubber line have not done that yet. Read the first post.
     
    wandi harry likes this.
  10. Happydaze
    Joined: Aug 21, 2009
    Posts: 1,054

    Happydaze
    ALLIANCE MEMBER

    Not seen any mention of bench bleeding and the master has been swapped at least once and also removed (I assume) from the booster when the clearance was checked, so is it 'bench bled' each time? ie do we know for sure there's no air trapped in the master - small principal as the caliper bleeders holes mentioned earlier, but usually no means of getting it out other than by temporary re-orientation.

    And I've reread the first post ;) but not re-read the whole thread. Don't bite the hand!!!!!!!!

    Chris
     
  11. hotrodhomework
    Joined: Aug 23, 2006
    Posts: 99

    hotrodhomework
    Member

    We are
    Bench bleeding each time every master is changed. We had a young helper that let the master go empty while we were bleeding as we were talking it over he admitted that he did so that is where the air came from. It is the smallest things that are over looked that can bite you. I know it is a lot to read. I apologize for the hand biting
     
  12. Check this out ,,,
    If / you stuck a gauge in and get 900 psi
    If/ you swapped to 1” bore and increase pressure to 980
    If/ you experience better low speed but poor hi speed slowing with that swap -

    Then I believe that you’re looking at a friction problem. Check the rotors well, check the pads.
    Look for glazing and you might even refinish the rotors. Look for fluid stained pads,,,
    Try new better pads they are quick and easy, $25.00 usually.

    You can bet your ass that helix kit has nothing but the absolute cheapest parts available to the human race.
     
  13. nunattax
    Joined: Jan 10, 2011
    Posts: 2,384

    nunattax
    Member

    with my system everything new it took a while for the pads/discs to bed in.not 100%of the pad surface in contact with the discs.got better as the miles went up.feel fine now.combination of fatman/GM calipers 11" vented discs,Kugel pedal assembly,8"double booster ,1" bore master cylinder
     
  14. Sure glad there was discussion, and the helper admitted the master going empty. I ran in to that too often when I was working. People were afraid to admit something for fear of getting in trouble, and I always used to tell them that we're just trying to find the root cause, and correct the problem, not lay blame.
     
  15. hotrodhomework
    Joined: Aug 23, 2006
    Posts: 99

    hotrodhomework
    Member

    Update installed the up28 vacuum pump that was recommended and Drumroll



    It didn’t help. Still crappy brakes.
    My friend order new master and booster. He is going to try “name brand” set up.
    I am going say it is not going fix it but I will help him try anything he wants to do. I do not think 900 psi enough to stop the car. I would like to see 1100 to 1200 psi at the calipers. The only thing I know that can produce that kind of pressure with this set up is a hydroboost but he will not try one because he is not done with the vacuum booster setup he has got to try it one time Talk about throwing parts at something.
    My hands are tied on some of the stuff I would like to do as in turn rotor, new pads and turn drums new rear shoes.
     
  16. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,898

    gimpyshotrods
    ALLIANCE MEMBER

    I have Hydroboost on my Falcon. If you were not wearing your seat belt, you'd go through the windshield.
    IMG_20181104_152153.jpg
     
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  17. Shadow Creek
    Joined: May 14, 2014
    Posts: 227

    Shadow Creek
    Member
    from Summit, TX

    @gimpyshotrods is that a mustang unit? I’m trying to decide which hydroboost unit to run on my project
     
  18. Pads are cheap,,,,
    And easy
    And 900 psi should stop a car
     
  19. jimmy six
    Joined: Mar 21, 2006
    Posts: 7,922

    jimmy six
    Member

    I'm guessing 53 Mercs had 11" rear brakes. When I replaced the rear end on my 56 I told the shop to find 11" for the 8.8. They came on F-150's and are bolt on and wider. I took out the 1" wheel cylinders and replaced with 15/16" My pedal had a 5-1 ratio and I used a 7/8" MC and true 4 piston calipers.(Wilwood) No need for a power assist vacuum can.
    You also need to adjust your prop valve to slide the rear tires on fast reaction then back it off. Good Luck
     
    48fordor likes this.
  20. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,898

    gimpyshotrods
    ALLIANCE MEMBER

    GMC.
     
  21. 49ratfink
    Joined: Feb 8, 2004
    Posts: 17,984

    49ratfink
    Member
    from California

    "Corvette style" master cylinders are 4 wheel disc master cylinders. you may have issues beyond that.
     
    bobss396 likes this.
  22. The only difference between disk and drum masters, given the same bore size, is reservoir size.
     
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  23. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,898

    gimpyshotrods
    ALLIANCE MEMBER

    Truth.
     
  24. sunbeam
    Joined: Oct 22, 2010
    Posts: 5,082

    sunbeam
    Member

    Is the booster check valve OK . It should lock in the highest vacuum the system has seen sense the last time the brakes were applied deceleration vacuum will be higher than the 14" at idle.
     
    Last edited: Aug 30, 2019
  25. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,898

    gimpyshotrods
    ALLIANCE MEMBER

    Unless it has a big-assed vacuum leak!
     
  26. Did you ever measure the line pressure generated with the hydro boost?
    He’s at 900 psi (at the caliper I’m guessing) and still can’t stop.
     
  27. BigChief
    Joined: Jan 14, 2003
    Posts: 2,082

    BigChief
    Member

    Did you pull the MC off the booster and verify that the booster push rod is adjusted correcly for minimal gap?

    Also some of the MC have inserts that fill the relief in the MC piston for the booster pushrod to sit in/engage. If there's too much gap you wont get enough stroke inside the MC regardless of pedal stroke. ..and the booster can fool you because you wont feel the excess free pedal caused by the excess gap. Verify that you have almost instant action in the MC when you move the pedal.

    Sent from my SM-G950U using The H.A.M.B. mobile app
     
    DIYGUY likes this.
  28. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,898

    gimpyshotrods
    ALLIANCE MEMBER

    Over 1200psi.
     
    David Gersic likes this.
  29. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,898

    gimpyshotrods
    ALLIANCE MEMBER

    See post #44.
     
  30. brigrat
    Joined: Nov 9, 2007
    Posts: 5,338

    brigrat
    Member
    from Wa.St.

    In my web investigation of brake line pressure the number 1200# comes up a lot as a standard pressure to achieve. It would be nice to know what weight vehicle that would apply to. Seems to me a much lighter car/truck or hot rod would work just fine with a little lower pressure assuming that number was meant for a factory produced passenger car or truck................................
     

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