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Wrencher Extraordinaire
2005 K1200LT
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Discussion Starter · #1 ·
Just finished my 2 year interval full system brake fluid flush on my 05 with 166 K+ on it. Even though I replaced the rubber lines years ago with Teflon/SS lines I still see a need, at least in the South, for a full flush every 2 years.

I measured the water content of the reservoirs in the wheel circuits and found the front was at 2% (not bad) but the fluid that came from the calipers was at 4% (bad). Like wise the rear wheel circuit reservoir was at 3% and the caliper fluid was 3%. The control circuit reservoirs were both at 4%. Now most of the time the bike was just sitting this year due to my back surgery but last year I did get quite a few rides in over the year.

This was a pain to do and it took me most of the day (8-3) but part of it I had company. A wayward humming bird decided to join me and fly laps around the ceiling of the garage. Finally lured him down to the top rack of the LT with a feeder, then moved the feed to a hangar on the garage door and he was gone. As I finished up cleaning the garage, moving my BMW convertible back into the garage and shifting the LT back to the double garage, the little bastard flew back into the garage again before I could close the door.

Once again the importance of doing regular fluid flushes cannot be over emphasized. My LT is 18 years old and the brakes have never had an issue.
 

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John, this is a good reminder to all members having these iABS modulator (with servos).

Since new, I do a full flush every year for the wheel circuits (these are vented to outside air) AND every 2 years for the control circuits. The dealer only did it the 1st time when the bike was 1 year old and still under warranty.

Later on (2006 and 2007) BMW published 2 Service-Bulletin(s) about extending this strict schedule above to 4 years for control circuits. I tried once for 4 years , however the result was not so good with pretty dirty fluid coming out of the control circuits bleeders. So I went back to the original strict schedule. I also execute the ABS mode several times during the riding season (about 5 months here) on a gravel road for a few braking applications.

After 20 years and 98,000 miles I still have the original ABS modulator, so It seemed to have served me to take care of it.
 

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John, this is a good reminder to all members having these iABS modulator (with servos).

After 20 years and 98,000 miles I still have the original ABS modulator, so It seemed to have served me to take care of it.
Guys, I can't say enough about how you have helped me and my LT. I was a line mechanic in a long since past career. I get most of what experience you pass along. There has been a bit of a learning curve, but it's been easier with your help. Thanks probably isn't enough, but please know how much your help is recognized. Thanks...
 

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2003 BMW K1200 LT (88K on 2020/08/13)
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+1 @Remy:
I too am grateful for the Experience, Knowledge and love so generously shared here, especially from @jzeiler , @beech , @sailor , @kbob12 and so many others. I have moved on from my 2003 K1200 LTE to a 2015 K1600 GTL and will be selling the LT after I add some of the items I've acquired for it. Again, thanks to the few for their imput and the entire community for the love and laughs.
 

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Yeah John I found the same thing with water content. I think my ABS died because of the heavy rain period we have had. Even though I wasn't riding and the bike is always under cover the moisture content in the air was off the charts. I would go down to the bike and it was wet all over. That ABS drain just sucks in the moisture. Two years is way too long and I think if you live in a region that has high humidity like the tropics you almost need to flush every six months.
 

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Can you elaborate on what that involves? I assume you're intentionally trying to lock up the wheels under hard braking to see if the ABS computer releases the wheel(s)
Assuming there is no dash warnings about ABS being defective AND ALSO assuming you know the history of your bike (has ABS module been removed by previous owner?).
Of course , If your ABS is defective you will fall down doing this procedure - you have been warned ;-)

1) go on NOT BUSY large gravel parking or gravel road,
2) get up to a speed you are comfortable in straight line - I do it between 20 and 30 MPH (30 to 50 Kmh)
3) apply a good pressure to both brake lever / pedal to force brake to lock-up in ABS mode , then release after a few seconds when you have felt the lock-up and the ABS pulsing.

Doing the above on dry asphalt is extremely difficult (lock up) and very hard on the tires, hence the gravel road is the best / easiest way to achieve this. Of course I always choose a gravel surface that is packed and not too deep , otherwise you will be fighting the steering like if you were riding in deep sand.

NOTE that on some BMW models the rear pedal is separate (not linked to front) so you can test Front and Rear individually in 2 test runs.

The goal is not only for your practice / familiarity how the ABS system will pulses , BUT MAINLY to activate some valves / fluid paths that remain unused if ABS is never activated. On these iABS with servos, it is better in my opinion to regularly activate the ABS mode. I do it at least once every 2 months during riding season.

During the winter when bike is parked in heated garage for 6 months, about at same 2 months interval with a fully charged battery: I turned ignition ON, wait 6 seconds (internal ABS check), then I apply both brake lever / pedal individually for about 3 seconds each to move the servos motors internally and force pressure.
 

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Wrencher Extraordinaire
2005 K1200LT
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15,592 Posts
Discussion Starter · #8 ·
Sorry John, I typed up this great response earlier in the day but then forgot to post it. Better late than never.

Can you elaborate on what that involves? I assume you're intentionally trying to lock up the wheels under hard braking to see if the ABS computer releases the wheel(s)
I presume he is just doing that for self satisfaction that the system works. There is no maintenance benefit from doing that as it does not exchange any fluid as the ABS solenoids just pull the check ball back to release the brake pressure.

Rectangle Slope Font Parallel Schematic
 

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Sorry John, I typed up this great response earlier in the day but then forgot to post it. Better late than never.

I presume he is just doing that for self satisfaction that the system works. There is no maintenance benefit from doing that as it does not exchange any fluid as the ABS solenoids just pull the check ball back to release the brake pressure.
John, thanks for the reminder on the function diagram - I had seen it many years ago but I forgot half of its details with age ;-)

In any system involving fluid , solenoids , valves, I always assume it is better to move these parts once in a while. Even more so when there is a risk of humidity and internal corrosion as we have seen on these defective ABS units once opened. So in case of doubts of the exact consequences of not doing it , I will continue my testing / execution routines as long as I have an ABS system on any vehicle.
 

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2004 K1200LT
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..... , I will continue my testing / execution routines as long as I have an ABS system on any vehicle.
I have to admit the gravel road test does make me curious now. I really hadn't even considered it before. I'm going to try it, at least once, and if for nothing else to satisfy my curiosity. Thanks for the tip.
 

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I have to admit the gravel road test does make me curious now. I really hadn't even considered it before. I'm going to try it, at least once, and if for nothing else to satisfy my curiosity. Thanks for the tip.
In addition to my justifications mentioned in previous posts above, you have to keep in mind that I was a civilian flight instructor for 7 years - about 2500 hours of flight between 1979 and 1986. This background alone justify my habit to practice emergency maneuvers AND ALSO to always learn everything about the systems of any machine (with wings or with wheels).
 
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