Page 1 of 2 12 LastLast

Thread: Brake Riddle

  1. #1

    Default Brake Riddle

    I have Gen 2.5, It's has spongy brakes, I have literally changed 95% of the brake system

    - New Master Cylinder, did bench bleeding
    - All new calipers
    - Pads are newish
    - Bled per the manual farthest side first and so on. Bled the proportioning valve too
    - Made sure there are no leaks

    Still have spongy brakes, brake travels almost halfway before it engages. I'm clue less, what else can i do?

    Thanks
    Gen 2.5 Montero Endevor
    E46 M3
    2007 Acura MDX
    1987 Honda Super Magna
    Royal Enfield 500
    ZRX 1200R

  2. #2
    Join Date
    May 2011
    Location
    Utah
    Posts
    6,445
    Which brand and composition are the pads? And yes it matters.
    1998 Montero with winter/locker package with Old Man Emu springs/torsion bars/shocks, ARB winch bumper, 33x10.50 km2's, aluminum roof rack with ARB awning

  3. #3
    Join Date
    Aug 2015
    Location
    Indy
    Posts
    402
    I'm fighting the same thing. All pads, rotors, calipers, and master cylinder have been replaced. I've used easily over a gallon flushing and bleeding the setup.

    Worst feeling pedal i've ever experienced. Feels somewhat like a bad booster, i get better pedal if i pump once every stop. Unfortunately, it doesnt show any of the other signs of a bad booster. And a booster isn't something you just throw at a truck.

    Utterly maddening.

  4. #4
    Join Date
    Apr 2015
    Location
    Michigan USA
    Posts
    400
    Have you replaced the flex lines?
    1998 Montero Gen 2.5 C

  5. #5
    Quote Originally Posted by jeep-N-montero View Post
    Which brand and composition are the pads? And yes it matters.
    I used Akebono pads all around.
    Gen 2.5 Montero Endevor
    E46 M3
    2007 Acura MDX
    1987 Honda Super Magna
    Royal Enfield 500
    ZRX 1200R

  6. #6
    Join Date
    Aug 2015
    Location
    Indy
    Posts
    402
    Quote Originally Posted by freewayross View Post
    I used Akebono pads all around.
    It doesn't matter for your symptoms. Brake pads used do not affect the point at which the pedal "engages," no matter what you might read on the internet.

    You have a hydraulic/pedal issue, as do i. Salonika's idea might be worth checking. Doesn't apply to mine unfortunately. Wish it did. My lines are nice and not noticeably expanding or ballooning at all with my wife standing on them with me under the truck.

  7. #7
    Join Date
    Jan 2017
    Location
    North Alabama
    Posts
    38
    If you've replaced everything and thoroughly bled the system (as you both have indicated), the next logical step is to test the brake booster. Here is a simple procedure:

    http://ssbrakes.com/attachment/85569...0Diagnosis.pdf

    If it is not the brake booster, then I would start looking at the ABS unit (and I know nothing about that!)

  8. #8
    Join Date
    Apr 2015
    Location
    Michigan USA
    Posts
    400
    I’d have it power bled before I did anything else. I’ve never experienced a failed booster, but I was just reading that they shouldn’t create spongyness. The booster does its thing between your foot and the master cylinder, so if it fails, it should just make a stiffer pedal sort of like pushing the brakes with engine off (that simulates a total booster failure, right?). I’ve also always wondered about bleeding with ABS. I’ve never replaced a master cylinder on a car with ABS, but I worry about the day I need to. There are a lot of passages in that unit that I can see air getting trapped in. Funny thing is, the FSM doesn’t call out anything special for it, so maybe it’s no big deal.
    1998 Montero Gen 2.5 C

  9. #9
    Join Date
    Aug 2015
    Location
    Indy
    Posts
    402
    Quote Originally Posted by Salonika View Post
    I’d have it power bled before I did anything else. I’ve never experienced a failed booster, but I was just reading that they shouldn’t create spongyness. The booster does its thing between your foot and the master cylinder, so if it fails, it should just make a stiffer pedal sort of like pushing the brakes with engine off (that simulates a total booster failure, right?). I’ve also always wondered about bleeding with ABS. I’ve never replaced a master cylinder on a car with ABS, but I worry about the day I need to. There are a lot of passages in that unit that I can see air getting trapped in. Funny thing is, the FSM doesn’t call out anything special for it, so maybe it’s no big deal.
    ABS is another thing i was thinking of. On a lot of vehicles, there's a way to cycle the system in order to bleed it, otherwise you'll never get all the bubbles out.

    The only reason i was thinking the booster was that the pedal sinks based on RPM, and the booster is the only part linked to the engine in the entire setup. I have a "higher" pedal in cold mornings when the truck idles at 1500rpm than i do when it's dog days of summer and it's idling around 600-750rpm.

    I'm a bit annoyed because i did the entire overhaul because it felt like crap to begin with. And it feels like crap after. Interesting tidbit: Reading threads on FJ80s with bad brake pedal, it sounds like in their world, the load bias adjuster causes a lot of problems for them once their trucks are lifted. My truck is fairly high, and the front is sagging a bit, so assuming it's serving the same function on the Gen2.5 as the FJ80, i could definitely see that causing issues.

  10. #10
    Join Date
    Jan 2014
    Location
    Phoenix AZ
    Posts
    7
    If you replaced the master cylinder, you need to make sure the depth of the Piston in the master cylinder and the length of the brake booster rod are within specs. I belive the gap between them is only a couple millimiters, check the factory manual. Too big a gap makes the pedal feel spongy. I had a booster fail before and the symptoms were the opposite of yours, the brake pedal was really hard.

Page 1 of 2 12 LastLast

Posting Permissions

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