Non Typical Servo Problems.

[Rastaossie]

This has been done to death but symptoms are not exactly typical so before stripping the whole thing out got to give it one try. Here goes.
2003 Servo ABS 4 spark 1150GS
Start bike move off ABS arms, touch back brake, instant solid triangle 4 hz flashing brake failure. Fek sez i.
Restart try again same result. Nail bike around block stamping on brakes. Front servo whine, all good, back no servo residual brakes, Solid triangle flashing Brake failure.
Bleed all brakes and servo unit, using excellent guide posted here somewhere. Test switches, test brake light.
Switch on, touch back brake, servo whine brakes, Hurrah! Front brakes good. Start engine move off ABS arms, lights go off. Louder hurrah. Stop roll backwards to initial position, hold back brakes on, servo cuts out lights come back. Boo-Hoo. Stop engine, turn back on, repeat procedure with same result, Servo both ends, abs arms, but hold back brake, lights come on.
I can hold the brake till the light shows, if i release immediately lights dont stay on. Thinking, bad hoses? dodgy pressure sensor? Where is that? Buy Triumph? Anyway any help appreciated. Stay upright.

 

[DrFarkoff]

basically BMW should never have removed the old ABS II system, but, that's just how I feel

If you have any problems basically you are placing your trust in a small PCB and a chip to initiate the servo assistance!

I have had so many of these things come by my place some of which had fluid that was a millennia old because people either were not advised to change the fluid or thought they were saving money

Some of them had decent brakes then suddenly changed to residual, Some had full power brakes every time you touched them and not the reduced power that they should have below 5km/h EQUALS Bollick / Tank interface! NOT GOOD

Some had proper front brakes and wouldn;t operate the back and vice versa etc etc etc There are many combinations

All I am trying to make you aware off That these brakes are great when working correctly

But EXTREMELY FRIGHTENING when they fail

Do you really want to trust in something that is there to stop that isn;t working

Good Luck

There is a post in the Font of all wotsit about removing and cleaning your plunger but other than that you have flushed the system and made sure the brake switches are working (Servo ABS switches are closed circuit at rest and open circuit when brake applied )

 

[warmshed]

When you put your front brake on, when not moving, you should hear the servo whine for the front brake, then with a bit more movement of the lever the whine should change I believe indicating that the rear brake is operating too. Does you bike do this?

 

[Rastaossie]

Putting the front brake on and holding, then the back, no lights. Release front, fail lights on.
Thanks for prompting that memory. Just think that if we made it we can fix it and it's designed to work, so should. Also drive a car most days with servo brakes so just ripping it out seems like an admission of failure. Of course that doesnt take into account that the Bavarians may have designed the thing badly, not something we should discount despite their self proclaimed infallibility.

 

[Steptoe]

You aren't going to know what it is until someone plugs in a diagnostic reader. Anything else is a random guess.

Far too many servo problem options to pick out the single cause over the internet.