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Technical m/c and or brake booster issue

Discussion in 'The Hokey Ass Message Board' started by c/h, Apr 20, 2019.

  1. c/h
    Joined: Jul 29, 2008
    Posts: 410

    c/h
    Member
    from iowa

    well all brake system is new.
    question is I have no brake pedal when engine is running pedal goes to floor with no resistances.
    engine off I have pedal with resistance.
    for mopar .
    also can any one identify whose makes the booster and master ? bought off ebay as a kit sat for 2 years while I got my truck done then this.
     

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  2. Doublepumper
    Joined: Jun 26, 2016
    Posts: 359

    Doublepumper
    Member

    Sounds like the booster may be the problem. There is a valve in them that can can go bad causing the symptom you're describing.
     
  3. paintman27
    Joined: Apr 23, 2011
    Posts: 254

    paintman27
    Member
    from new jersey

    watching this, as I have the same exact problem. Engine off pedal is firm. engine on pedal drops to the floor. Can't find a leak anywhere.
     
  4. 56premiere
    Joined: Mar 8, 2011
    Posts: 1,428

    56premiere
    Member
    from oregon

    Push rod length is my guess. Just what mine did
     
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  5. BJR
    Joined: Mar 11, 2005
    Posts: 5,549

    BJR
    Member

    Don't know about your brakes, but your throttle cable is frayed and could stick it wide open. I would fix that before you drive it.
     
  6. c/h
    Joined: Jul 29, 2008
    Posts: 410

    c/h
    Member
    from iowa

    good eyes
    been taken care of
    thanks
     
  7. patterg2003
    Joined: Sep 21, 2014
    Posts: 515

    patterg2003

    Good catch. The eagle eyes on this forum are amazing. Time and time again guys notice something out of place that is not the subject of the photos. Often it is safety related and the comments are usually helpful. It is great see.
     
    nunattax likes this.
  8. paintman27
    Joined: Apr 23, 2011
    Posts: 254

    paintman27
    Member
    from new jersey

    As long s were piccking apart your truck LOL,You might also want to put a grommet in the firewall where those wires are comming through by the dizzy.
     
  9. guitarguy
    Joined: May 26, 2008
    Posts: 113

    guitarguy
    Member

    I had the same issue on a Dart I converted to power brakes. I replaced the booster and all was well. Took me a bit to figure it out though.
     
  10. Too short will easily give those symptoms. If you can adjust it, go like 1/8" at a time and keep track in case you go too far.
     
  11. V8 Bob
    Joined: Feb 6, 2007
    Posts: 2,422

    V8 Bob
    ALLIANCE MEMBER

    What is the pedal ratio?
     
  12. c/h
    Joined: Jul 29, 2008
    Posts: 410

    c/h
    Member
    from iowa

    went out and checked have good vacuum from intake. Then unhooked vacuum line to check valve let sit 30 second and undone the check valve and the canister is holding plenty of vacuum. Still or bad or possible m/c.
    or length of rod?
    booster is brand new been sitting for close to 2 years but could be defect also.
     
  13. c/h
    Joined: Jul 29, 2008
    Posts: 410

    c/h
    Member
    from iowa

    sorry don't know ratio. Bought the kit from the ram man brake guy.Email him haven't heard back.
     
  14. gene-koning
    Joined: Oct 28, 2016
    Posts: 1,213

    gene-koning
    Member

    Those small diameter brake boosters have caused a lot of problems over the years. I've seen a lot of them suck the brake pedal to the floor, and I've seen a lot of them where you can hardly push the pedal at all. The ones that push real hard,k then when they start to move, they go all the way to the floor are really fun to deal with.

    If the brakes function without vacuum assistance, the problem is probably that booster. Getting a good small diameter booster is a crap shoot. I would look into a larger diameter brake booster if at all possible. Gene
     
  15. c/h
    Joined: Jul 29, 2008
    Posts: 410

    c/h
    Member
    from iowa

    well took it out looks like this is the problem broken plastic missing and when I hooked to vacuum you can here the
    leak when pushing in the plunger.
    tried make contact with the company I bought from nothing back.
    any input on what booster I should use. Honest prefer the one on the truck just because it bolts up and no changes needed but im not sure what its out of. mopar I know that but ram man never got back to me .
    thanks
     

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  16. c/h
    Joined: Jul 29, 2008
    Posts: 410

    c/h
    Member
    from iowa

    well after installing a new master cylinder and a brake booster I have exact same problem with the floor pedal going to floor while truck is running.unhook plug vacuum line have pedal. Nothing changed .
    its all brand new .yes made sure rod is in correctly from booster to master.
    defective caliper? there are no leaks under and of the lines or fittings.
    Im stumped and have 2 full time mechanic stumped also. Called speedway said it was rod issue.
    made the adjustment no result.
    brake are in the back also have a emergency set up I removed that because hit my springs don't know that has anything to do with it
     
    Last edited: May 4, 2019
  17. Doublepumper
    Joined: Jun 26, 2016
    Posts: 359

    Doublepumper
    Member

    New stuff...if the brakes have been bled (with engine off), it would seem the push rod is still too short. That, or a defective booster/master are the only things I'm aware of that can cause this. But, there's a whole lot I'm not aware of:D
     
  18. c/h
    Joined: Jul 29, 2008
    Posts: 410

    c/h
    Member
    from iowa

    yes bleed engine off.
     
  19. c/h
    Joined: Jul 29, 2008
    Posts: 410

    c/h
    Member
    from iowa

    what about if I block the lines from master and plug them then see what I have pedal and start eliminating it from there.maybe keep adjusting rod?
     
  20. paintman27
    Joined: Apr 23, 2011
    Posts: 254

    paintman27
    Member
    from new jersey

    Like I posted previously. I have the same exact problem. I am convinced it is the front GM metric calipers that are the low drag version. I was going to try a quick uptake MC but it wouldn't fit in the bore of the 7" booster. I think my next move will be to swap out my front calipers to the olde style high drag.
     
  21. sedantudor
    Joined: Jan 28, 2012
    Posts: 50

    sedantudor

    Is that an adjustable proportioning valve hanging under the master cylinder? If so, is it adjusted correctly? Not likely the problem but an observation. I had a similar problem on my Ford and it turned out to be two problems. The first was a the fact that I did not install any residual check valves in the brake lines and brake was flowing backwards when the car sat for a while, but they are generally only needed when the master cylinder is below the calipers or mounted on the frame. The other problem was a misadjusted push rod on the master cylinder. Another thought would be check the vacuum source to make sure it is pulling an intake vacuum reading of about 18-22 in/hg.
     
  22. c/h
    Joined: Jul 29, 2008
    Posts: 410

    c/h
    Member
    from iowa

    good vacuum
    yes proportion valve .calipers well below m/c
    im going to go out plug my m/c and see if I have pedal if not il start adjusting the rod see what I come up with.
     
  23. You should be able to measure it.

    Is this what you’re working with?
    http://therammaninc.com/products/sh...100-FRONT-POWER-DISC-BRAKE-CONVERSION-KIT-390

    914E864A-DD11-4668-B69A-1ACE56A7BD80.png

    Maybe I’m an asshole,,,
    No way I’d deal with a company that can’t even spell what they are selling.

    Now, brake fluid isn’t hard to outsmart. If it’s got you and 2 other mechanics stumped,,, you guys are operating under assumptions that are incorrect. Got back to square 1 and verify the components are GOOD. Assuming they or any parts are really good justbbecause they are new is a bad plan anymore.
     
    Last edited: May 4, 2019
  24. Scrapin’Metal
    Joined: Mar 19, 2018
    Posts: 27

    Scrapin’Metal

    Had the same issue. Master cyl was leaking and booster was bad. Replaced with new reman master and booster, had pedal with engine off, started engine and pedal goes to floor.
    Good vacuume and no leaks. Tried pulling vacuume on booster and it would leak down. Replaced both master and booster and pedal was up where needed.
    Look to see if booster does hold vacuume.
     
  25. c/h
    Joined: Jul 29, 2008
    Posts: 410

    c/h
    Member
    from iowa

    I feel stupid but guess were all learning.
    turns out I had adjustable rear calipers on back had to take the adjustable out of it cause it made contact my springs
    after blocking off rear line master fronts and pedal work like it suppose to.
    off to buy no adjustable rear brake calipers. Boy wasn't thinking .
    thanks to all who weighted in with advice very much apprenticed.
     
  26. That’s one problem,
    I’d think that would give you the same pedal with engine on or off .
     
  27. c/h
    Joined: Jul 29, 2008
    Posts: 410

    c/h
    Member
    from iowa

    hey guess whose back
    well installed new non e brake calipers. Bleed them and started engine and still hits the floor. Yes check rod from to booster good there.no leaks a any connection..im guessing next residual valve
     
  28. One of two things ,,,
    You really are not achieving a good pedal with engine off.
    OR
    You have too much mechanical leverage and the booster adds even more. The line pressure is fine but telling stories to your foot because the kit manufacturers state it takes 2fingers pressure to stop your truck.

    Get a brake pressure gauge and see what’s actually happening at the calipers. Based on what you’ve been saying here and again based on your assumptions you should see something well above 1200 psi with the engine off , and when you start the engine the gauge pressure will fall off as the pedal goes to the floor.
     
  29. Garpo
    Joined: Jul 16, 2016
    Posts: 140

    Garpo

    There must be dozens of brake threads on the Hamb. Seems to be a lot of guess work and assumptions..
    With engine off the booster is really just an extension of the push rod - a solid link.
    If the pedal is solid with engine off, adding assistance from the booster will NOT take it to the floor; but the assistance should take the pedal down about an inch. Just like pushing 50% harder.
    Brakes are the sum of all the parts, every part needs to be fitted and adjusted correctly. As in Henry's old Flathead service notes "diagnose, don't guess"
    Jumping to conclusions and changing rear calipers wasted time and money without curing the problem.
    Need to work through the system quietly and logically to sort it. Will probably need another pair of experienced eyes to assist. Two heads are better than one.
    Remember it's not rocket science.
    Garpo
     
  30. c/h
    Joined: Jul 29, 2008
    Posts: 410

    c/h
    Member
    from iowa

    well pedal rod length incorrect under dash .corrected that and im in business
    thanks to all.
     
    olscrounger and David Gersic like this.

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