Results 1 to 4 of 4

Thread: Brake pedal randomly goes hard on hills & lose braking power - 110 County

  1. #1
    Join Date
    Mar 2008
    Location
    Outer Sydney
    Posts
    478
    Total Downloaded
    0

    Brake pedal randomly goes hard on hills & lose braking power - 110 County

    Good evening all,

    1984 110 V8

    My brake pedal randomly goes hard, and braking power becomes a lot less. Although it is mostly random, I have noticed that it happens much more often when braking to a stand-still down a hill. It gave me a scare today, but I think I have learned a bit from it – Trying to brake to a stand-still on a steepish and wet hill, the pedal went hard, and I had very little braking force. I had to push the pedal very hard, but I still had little braking force when suddenly the front wheels locked up! Luckily I was only doing about 15km/h. I can’t be real sure, but it almost felt like the back brakes were not working. Could this be a symptom of a brake proportioning valve issue? I understand that these limit the hydraulic pressure to the back wheels, but can they limit it too much? I also seem to get this issue when I am braking gently, then need to brake harder to come to a stop – the pedal goes hard and I lose braking power.

    The braking system is in pretty good nick:
    - New pads up front and shoes at rear. Shoes are installed correctly, with leading and trailing in correct spots.
    - The back shoes are adjusted pretty-well. The brake pedal sits high, and doing the ‘double tap’ on the brakes (under normal driving) makes no difference to the height of the brake pedal.
    - The vacuum booster is brand new – old original one developed a massive and sudden leak. The preload on the pushrod has been adjusted.
    - Newish brake master cylinder, rear wheel cylinders and all brake hoses.

    Many thanks,

    Edward 😊

  2. #2
    Join Date
    Apr 2016
    Location
    Melbourne
    Posts
    4,203
    Total Downloaded
    0
    Just sounds like either brake booster has a leak, can hold some vacuum, but not create enough once you use some .. so like a slow leak.

    Or, a small leak from the vacuum pipe to the booster.
    Arthur.

    '99 D1 300Tdi Auto
    '03 D2 Td5 Auto

  3. #3
    Join Date
    Mar 2008
    Location
    Outer Sydney
    Posts
    478
    Total Downloaded
    0
    Thanks mate!

  4. #4
    Join Date
    Sep 2008
    Location
    Geelong, VIC
    Posts
    4,442
    Total Downloaded
    0
    LT95 with vacuum CDL?
    If so, the hoses to/from and the diaphragm inside are other things that can leak vacuum. Diaphragm test is easy by putting a fresh piece of hose on a connection and sucking on it. If it builds vacuum its OK. Will likely taste like petrol though - Isuzu's are nicer
    Being a V8, its only engine inlet vacuum not a proper vacuum pump AFAIK, so also anything between the engine and throttle butterfly.

    To test if if its a vacuum issue, while stopped with foot off the brake let the engine idle for a 30secs or so then switch it off. Wait about a minute and then you should still get a couple of decent applications of the brake before the pedal goes hard.
    If the pedal is already hard first time then the vacuum has already gone. You'll need to track the leak down.

    Remote chance it could be a collapsing rubber vacuum hose to the booster - collapsing under the increased vacuum of engine braking downhill. Pretty hard to pick so if the booster test above is OK I'd replace the hose to be sure. Make sure its proper vacuum hose as it's designed not to collapse.

    Steve
    1985 County - Isuzu 4bd1 with HX30W turbo, LT95, 255/85-16 KM2's
    1988 120 with rust and potential
    1999 300tdi 130 single cab - "stock as bro"
    2003 D2a Td5 - the boss's daily drive

Tags for this Thread

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
  •  
Search AULRO.com ONLY!
Search All the Web!