K1200S Brake-Servo problems

[mark5lam]

Recently, some of my riding buddies have been telling me that my brake light appears to be coming on more than normal. Now (more recently), I've been getting a rapid flashing "brake failure" light at start up. With the rapid flashing light, there is no servo assisted power to the brakes until the light goes out after initially riding up to a mile.
Today I noticed that sometimes when I touch the brake handle, not only does the brake light stay on, but the servo continues to run and the brakes actually drag while riding.
The whole system seems to be progressively and systematically failing.

The bike goes in for the 12K service this week. Not only do I need to get this problem fixed, I think the dealer should replace my brake pads under warrantee considering the premature wear has been caused by the system faults.

Anybody else have this problem or any insights here?

[robertbentley]

Hi
I had a problem yesterday with my K1200S brakes. Usually, when the bike is started, the "BRAKE FAILURE" light flashes once a second, and stops flashing when I have gone a couple of yards. Yesterday, it flashed 4 times a second, and the brake servo was not working. This is "limp home" mode, where the brakes are not assisted, and ABS is not available. I called BMW and they told me that the reason for this was that the computer could not complete it's tests on the braking system. The usual reason for this was that the rear brake was jammed on, or if not, the rear brake switch was on, fooling the computer to think that that the rear brake was on.
I checked the small rear brake switch, and as the guy suggested, there was a small stone lodged in the metal strip of the switch. Once it was removed, the bike returned to it's normal operation.
The tech told me that this was a common fault, and BMW really should have put a rubber boot over the switch.
Rob Bentley
ENGLAND

[mark5lam]

That's good info. Thanks.
In my case, the brake handle switch was sticking (occasionally and ever so lightly). Hardly noticeable but enough to remain engaged and cause an ABS/Servo fault.
The tech stated he had to partially disassemble the brake handle and adjust an internal grub screw. This seems to have fixed the problem.

[robertbentley]

Sounds like the same problem - but on the other brake. I belive that if the computer cannot complete the tests, (e.g. brakes are stuck on) it falls back into partial mode - where you don't get servo assistance or ABS.

All the best,

Rob

[sesand]

I have a2005 servo assisted abs and noticed a little rear wheel lockup on hard braking in a curve. I didn't think that was supposed to happen with abs so I tried to intentionally lock up the rear wheel in a controlled setting coming to a stop while only going about 25 mph with the clutch pulled in. The wheel locked up and there was a period where it sounded like a bucket of bolts rattling around. Is that supposed to happen? I thought the abs was supposed to kick in and disallow this. I don't have any warning lights on. Is this a problem with the servo?

[sesand]

I will now answer my own question: I talked to the mechanic who does the work on my bike, and he said some of the mechanical noises are from the servo ABS keeping the tire from completely locking up.

[Eka]

That rattling is probably rather from lacks in final drive, gearbox etc. Activated ABS brakes, release, brakes, release... in very quick cycles and at rear it's everything between engine and tire shaking. Noises from that is normal. Of course at front there is not that problem. Servo just makes some high tune whining.