Make It Stop! (Working On A BMW ABS System)

Back in June when we were returning home from a trip to North Carolina the front brake line on the K1200LT developed a small leak in the front brake line.  We made it home with no issues but in the last few miles I began to notice a different feel in the front brake lever.

I ordered a new front brake line from BMW Motorcycles of Atlanta and it arrived this week.  I spent the last 2 days doing my repair and cleaning up.  Well, actually today was just spent putting the body panels back on the motorcycle.  My plan was to replace the leaking line, then bleed the air out from the replacement and then flush the entire ABS system.  Flushing the ABS system is a maintenance item that should periodically be done anyway.  In the past I had flushed brakes but this would be my first time replacing a line and therefore intentionally introducing air into the system.  To replace the line easily I was going to have to remove the fairing from the motorcycle, or the parts referred to as “Tupperware”.  I’ve removed all these parts before during a 24,000 service so I wasn’t scared.  Usually I have to remove the engine spoiler and lower fairing, but not this time.  When you follow the directions in the Clymer’s manual it all goes smoothly.  It was tempting to not remove the fairing but it was obvious removing it would make things easier.

First, you need to understand something about the brakes on this particular motorcycle.  BMW uses a servo assisted integral ABS system.  That’s a lot of big words but it means the braking system is power assisted like a car, the integral part means using the rear brake will also begin to add front brake, using the front brakes will also add rear brake and the system is an Anti-lock Braking System.  It also has a front & rear control circuit (integral pump) and a front & rear wheel circuit (the calipers on the wheels).

Once I got the Magic Carpet naked the brake line replacement went pretty quickly.  Then it was time for the bleeding and flushing.  I got a lot of information from BMWLT.COM for the flushing.  My assistant, Donna, helped me for this part as you really can’t reach the bleeder and the brake lever for all of the work.  While bleeding & flushing the front, I accidentally let the funnel in the brake reservoir run dry.  I regrouped and we bled the air out making a foam in the catch jar and then all was good.  The old brake fluid in all 4 circuits had the color of iced tea so it really did need to be changed.  All 4 circuits now have that nice, nearly clear DOT4 brake fluid now.  So far I don’t appear to have any error codes appearing on the dashboard either!  Of course there were some “gotcha” moments too.  Some of the bleeders on the integral pump were a major pain to get to.  And for some reason, the bleeders on the front and the rear brakes used 2 different size wrenches.  The use of the brake funnel from Beemer Boneyard made this job a lot easier too.

Once the old hose was off, I looked for and found the suspected leak.  I cut the hose open in both known good areas and the suspected problem area.  The good area has a nice, round opening for the fluid to pass through and you could see the layers of rubber and braiding.  The suspected bad area was brittle, clogged and all black.  Oddly enough, I also think the bad area is where the Moto Lights had a short in the wiring and the wires had been zip tied to the brake line.

The job wasn’t as bad as I had feared but it’s not something I want to do all the time.  I can see why the dealer gets so much money for a brake flush though!

I’ve had the Tupperware off a few times before so I have a system for keeping track of all the torx screws.  But this time, when I put everything back together, I had 2 leftover torx screws.  At least I’m not OCD enough to take everything apart to see where I missed putting them in.

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Categories: Maintenance & Repair | Tags: , , | 5 Comments

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5 thoughts on “Make It Stop! (Working On A BMW ABS System)

  1. I am suprised that you didnt upgrade to Spiegler lines. That is a lot of money to spend on one line! I did not attend the MO Rally but there is rumor that some people died on the way due to the heat. Any truth to this?

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    • I considered Spieglers but they only sell them as a complete set for the entire system (not individual units like BMW) which is at least twice what I paid. If the OEM lasts another 10 years I’ll be happy. I haven’t heard of any heat deaths on the way to the MOA rally.

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      • I hope there wasnt. My friend told me there was a moment of silence for them. I have searched the internet but cant find any info. Maybe it was just a rumor. I hope you get another 10 for sure! We both know you wont keep it that long before you get something else 🙂

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      • Maybe I’ll keep her until she’s considered “vintage”. 🙂

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  2. Pingback: Why Is There Brake Fluid On The Floor? | Chris & Donna's Motorcyle Journeys

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