that doesn't sound good. do the brakes work ok whilst that's happening?
regardless, flush them now. do not ride it.
otherwise, possible bad pressure sensor? never really got into HOW it works. but it should stop when you let off. maybe its not reaching the required pressure. that scares me, like it could randomly apply or release pressure...? Mine did that once, and that was when I was flushing, and let way too much fluid out, because its always under presssure. (that was the final point I decided to remove)
we are here for you if you do tackle the servo removal. Just like tower.... I promise, its not too bad....it only took me a few hours after work. and then the next afternoon to clean up my mess. take your time don't get in a hurry. follow the wiring splicing instructions to the letter. will cost you zero dollars, minus supplies....I don't miss it... though I noticed last week, my gas tank still has the little sticker.
the ONLY difficult part in this.... when you get everything out of the way, and it comes time to pull the servo and connector..... there IS a feeling of being a bomb squad soldier diffusing a bomb. like, a no return point...when you actually snip the wires. some folks keep the little module intact, which is ok too, but I yanked it all. Take a swig of Newcastle, close eyes, and cut LOL
heres one I Printed this out.... detailed photos. basically, all youre doing... going from 4 brake lines down to 2. rear goes straight from pedal to caliper, and front goes straight from lever to calipers. instead of in/out of servo.
http://bmwtcnsw.org.au/techfile/R1150GS ... emoval.pdf
then use this simple wiring guide from the ukgser thread posted earlier. (note, look closely at wires, I was duped by brown/red vs just brown lol)
1) Remove the blue ABS relay from the fusebox. This will extinguish the 'Brake Failure' warning light on the dash and as a bonus can be used to operate the brake light !! (no need for new switches as in other methods )
2) Strip back the sheathing from the ABS multi pin connector - identify wires and connect as follows
a) Grey/White wire (tail light feed) Grey/Black wire (12v feed) cut both and join together - thats your tail light sorted.
b) White/Yellow wire (front brake switch) and Yellow/Green wire (rear brake switch). Cut these two wires and join them to link brake switches
Now the wiring to the redundant 4 pin ABS relay
c) Pin 1 - Connect white/blue wire
d) Pin 2 - connect the THIN solid brown wire in the loom to provide a ground ( careful here - there are several brown wires c/w coloured traces and a Thick brown wire)
e) Pin 3 - Find the Yellow/Black wire and the solid green wire. Cut and connect these together and then to pin 3 of the relay
f) Pin 4 - Connect grey/yellow (tail light feed) to this pin