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Thread: 2003 R1150RT brake saga and a question

  1. #1
    Registered User rogerc60's Avatar
    Join Date
    Oct 2018
    Akron, OH

    2003 R1150RT brake saga and a question

    This past November, after being away from motorcycling for almost 30 years, I bought a 2003 R1150RT. The bike looks and runs nice and the price was certainly right. The seller owns a vintage cycle shop (sells, repairs, and restores vintage 60's, 70's, and 80's bikes, mostly Kawasaki). Turns out he is not an expert on Beemers.

    The general warning light on the dashboard was flashing at 1 Hz, but the brakes had plenty of power. The owner told me a BMW mechanic he knows told him that since the brakes were working okay the system just needed a fault indication reset. Nothing else seemed to be wrong so I bought the bike and then went looking for information. I found BMWMOA and after reading some on the forums joined right away. You all have been a God-send!

    One of the first things I learned is the iABS on this bike doesn't have any kind of reset. Okay, so now I need to start troubleshooting.

    I couldn't make heads or tails of the light blink codes because the brake failure light never came on. Not even when I first turned the key. Figuring the bulb must be burned out I tore the front end of the bike apart to get to the instrument panel. But the bulb was not burned out. That's when I discovered the relay that drives that bulb; one of the previous owners obviously had pulled that relay out and tucked it nicely into a space at the side of the fuse box. Maybe he got tired of the continual click click click click click...

    Now that I have both bulbs operating, I am getting the normal sequence of flashes at key turn-on and then they settle into an alternating 1 Hz flash. Now we're getting somewhere. After reading on this forum about rotting rubber brake hoses and observing that my bike still has the factory rubber hoses, I decided to replace them with stainless steel and would diagnose the brake problem was while doing the replacement (hoping it's just low brake fluid level).

    So I bought a Galfer brake line kit, and finally got some time to dive into the job. Upon removing the rear reservoir cap on the ABS controller I realized just how fortunate I've been: there was no brake fluid visible. I could see clear to the bottom and it was dry. I have no idea how those rear brakes were working. BTW, the front reservoir has fluid, about 1/8" below the max indicators.

    I replaced the rear caliper hose and bled the wheel circuit. I don't see any leaks, and now that I have the rear wheel reservoir properly filled the general warning light has stopped blinking. I don't have the bike together yet so I can't do the roll-off test to see if the brake failure light stops blinking. Hopefully next week.

    So now I come to the question. I need to figure out how that rear circuit lost its fluid. My theory is that somebody who doesn't know how these brakes work tried to bleed the rear brakes by using the bleeder valve on the rear caliper and the control circuit reservoir near the brake pedal. ("How come the level isn't dropping in the reservoir? Oh well, it's clear and no bubbles coming out the bleeder valve so it must be okay!" Doh!) There are no signs of leaking brake fluid anywhere in the rear wheel circuit.

    Has anybody experienced anything similar. Is there some other explanation for that missing fluid that I might need to check into? Thanks for reading and again for all your help!

  2. #2
    MOA #24991 Pauls1150's Avatar
    Join Date
    Apr 2008
    south of Los Angeles
    Just a wag: the prior owner didn't know that bleeding the brakes requires the ABS module under the tank to be opened up and bled out too...

    If there was no fluid at all down there at the rear, I'd be suspicious of the integrity of the seal inboard of the pads.

    I've never tried this, but I wonder if the brake-check routine in the computer can be faked out by putting the bike on the centerstand and giving both wheels a strong spin...?

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