Bagger Brake Issue

Discussion in 'Wheels' started by HKSkully, Oct 29, 2011.

  1. HKSkully

    HKSkully Member

    the same part number for the brake light switches. Were not the earlier models 07 and up having the same type of "lean" heating condition in the exhaust? Even so much as to have HD sell plastic heat deflectors for the touring models.....

    Ran into this condition a short time back. Still awaiting the fix information.

    Have an issue with an 08 Ultra and its ABS (rear brake inoperative).

    It started with discovering that the rear master cyclinder was empty. Inspected brake hydraulics and didn't notice anything out of the ordinary and there was no signs of any fluid leakage or any past leakage.

    Rear brake pads also worn down to point of replacement (not wore out completely but yet the pads were in need of replacement). The rear brake caliper pistons were not extended to the point of causing the M/C fluid level to drop to zero.

    The brake line from the M/C to the brake switch was rubbed flat on one side (along the frame rail) due to the clutch cable but no leakage was detected. Installed rubber isolator to prevent further damage to line and notified customer of the lines condition.

    Re-filled M/C and opened rear caliper bleeder. Bled out rear brakes with no problem. Air was present till solid fluid came out. Removed pads from rear caliper and opened bleeder to depress caliper pistons with our caliper piston tool (designed to depress all pistons at the same time). Closed bleeder and installed new pads.

    Re-confirmed no air in system and topped off M/C. Road tested and all is good. No malfunction, no ABS light on and brakes operating properly along with brake light operating when rear brakes are applied.

    A few days later, the bike has a brake pedal that is hard as a rock (like stepping on a concrete block). It will not depress and the rear brakes will not activate.

    Removed rear brake caliper and verified proper pad fitment and placement of anti rattle clip. All is in order but the brake pedal still would not depress, even with caliper off of its mounting bracket and my fingers between pads (no pad movement).

    In re-examining the hydraulic system, the M/C is full and there is a slight moisture "leakage" of fluid at the rear brake light switch.

    Perhaps this is where the original fluid had leaked out but there were no previous signs of leakage at this area. The brake lights were operating from the foot brake pedal as it was depressed just days before but now they were no longer operating from it??

    I tested the wiring by jumping the BLS connectors with a paper clip and the brake lights came on.

    In scanning the ABS ECU system, the codes that were present were C1095 (Front Brake Swith Interrupt) and C1216 (Rear Brake Light Switch Interrupt). Cleared the system but C1216 returned as an active code. The ECU as well as the Brake ABS Controller was not recognizing the voltage output (their input) from the rear brake light switch being activated (The ABS controller had no idea that the rear brakes were being applied, even though the Rear Wheel Speed Sensor was greatly differing from the Front WSS, when abruptly slowing down, there were no additional codes other than C1216)???

    Re-installed rear brake caliper and loosened brake line at M/C. Pedal pushed down with little effort and fluid came out of the fitting under pressure as it would normally. Tightened that connection and loosened the fitting, feeding the rear brake hydraulic circuit leading into the ABS HCU and fluid came out under normal brake pressure as the brake pedal was pressed down normally.

    The brake hydraulics were operating properly to the HCU. Loosened the hydraulic fitting from HCU which feeds the rear brake caliper and NOTHING (Brake pedal will not push down and fluid will not exit loose fitting), not even with extreme foot pressure!

    Brake fluid hydraulic pressure is not going through the ABS HCU to the rear brakes and the bike has no rear braking action, as well as the brake pedal being hard and unable to be pressed down (at all)?

    The valves in the ABS HCU function in 3 ways:

    1. Pressure Hold; The apply valve keeps the release valve
    closed in order to isolate the slipping wheel when wheel slip
    occurs. This holds the pressure steady on the brake so the
    hydraulic pressure does not increase or decrease.

    2. Pressure Decrease; If the above "pressure hold" does not correct the wheel slip condition, pressure decrease occurs. The apply valve is closed and the release valve is opened and the affected hydraulic circuit is isolated from brake pressure. The excess fluid is stored in the
    accumulator until the pump can return the fluid to the master
    cylinder or fluid reservoir.

    3. Pressure Increase; After the wheel slip is corrected in the above pressure decrease mode, a pressure increase occurs. The ECU increases the pressure to individual wheels during deceleration in order to reduce the speed of the wheel. The apply valve is opened and the release valve is closed. The increased pressure is delivered from the master cylinder and will not exceed the pressure from the master cylinder.

    I believe that one of two problems exists. Either there is a serious fault in the ABS controller (no codes indicating difference in speed sensors) and the HCU and that the "Pressure Decrease" valve is stuck closed, thereby isolating (the rear brakes) and not allowing hydraulic pressure from M/C through ABS HCU to allow rear brake operation or that the rear brake light circuit hydraulic switch failed and an internal component of this switch travelled through the line and into the HCU and blocking fluid pressure.

    In either event, this is a situation that can cause serious and disasterous results. Especially occuring without warning. There should be a fail safe designed in the system to prevent this from ever happening. If the ABS HCU fails or becomes inoperative, the braking system should revert to non ABS braking.

    Will post the repair outcome when determined.
    Last edited by a moderator: Oct 29, 2011
  2. Jack Klarich

    Jack Klarich Expert Member

    This is a very good read I will follow this one, am looking forward to the answers