r1150gs adv no rear break

[romek]

hi from Morocco. Need some advice/help. My rear brake doesnt work.
2003 r1150gs adv with servo. Foot Microswitch works = brake light goes on, but abs pump doesnt. Front microswitch works = brake light goes on and abs pump works. Checked connections, barke bulb replaced in case. abs sensors seems to ok. Starting engine, first gear and go. All is ok until first brake. Trianglelight lights continuosly, and braik failure light flashing 4hz. Rear break doesnt work.. What to do? Sure I can continue ride and I will, but flashing lights doesnt make me happy. Thanks in advance for any help, greetings from Ouarzazat - Romek

 

[Packer]

First thing to try is switching off engine with key. Press down ABS button on right handlebar switch set and restart the engine so that the ABS is disabled. Do you have a back brake now?

If not when did you last check the fluid level in the ABS system? There are two black plastic filler plugs worked by an Allen key. The rear one is for the rear circuit. Unfortunately this is a tank off job but you have the quickly detachable fuel lines. I wouldn't do this in the middle of nowhere unless you have spare "o" rings for the connectors, they are very easily damaged if you aren't used to them. If the tank is full it may be a two person job, they are heavy!!!

If the front brake still works fine get some type 4 brake fluid and re-plumb the rear brake, the hose from the rear caliper will reach and attach directly to the rear master cylinder. Although the front and rear brakes are linked with the servo system through the rear brake pedal they have seperate fluid circuits but still be careful to check that your front brake is good!

Failing this disconnect the entire servo abs system. Look here

I've done this on mine, it's quite simple and straight forward, a couple of hours work. There is a risk that bleed nipples will sheer off. If they do bleed the brakes by slackening the union to the caliper as you operate the brake lever and then retighten before releasing the lever. Fiddlly but it works. If you are bleeding the front circuit cover the master cylinder as you pump the lever as it tends to spit brake fluid out of the reservoir and this can get on the paint which is bad news for the paint finish.

The brakes work brilliantly without the servo

Good luck.

 

[romek]

thanks for reply
turned off abs, still the same. Press foot lever and nothing. yesterday I bleed rear brake system including abs servo. Mean removed tank etc. btw fluid level on servo was ok for front and back circuit. Noticed that "brake failur" light dtsrts flashing after pressing lever bit harder, not only whe I hear microswitch click. Hope you understand me, sorry about poor english. Thanks again and waiting for more Romek

 

[Packer]

Your English is far better than my Polish

Just on the off chance, (and I'm sure that you will have, but) you have checked that there is still fluid in the rear master cylinder on the side of the bike?

When you bleed at the servo it uses the master cylinder fluid, when you bleed at the wheel cylinders it uses the servo fluid.

If there is fluid everywhere that there should be and no sign of leakage anywhere but the brake still doesn't work I would take the servo out of circuit for the rear brake because it sounds like a servo/abs failure.

Double check that the front is still working properly. In fact do the "no cost removal" process in the link I posted, you don't need any spare parts and you will have safe brakes. The last thing you want on a loaded GSA is brake failure coming down a mountain

If you have have the servo system repaired it is simple to re-install although I would never go back to that system now.

 

[romek]

Just on the off chance, (and I'm sure that you will have, but) you have checked that there is still fluid in the rear master cylinder on the side of the bike?

yep, there is

 

[Packer]

Ride without a rear brake and hope that the front keeps going or follow the servo bypass instructions, they really are fairly simple.

Good luck!

 

[romek]

thanks Packer, yes it looks very simple to do, and I'm almost ready to do it. Before last decision I'll try one more thing. In NO COST ... post there is info "Yellow/Green wire (rear brake switch)" Maybe is not bad idea to do shortcut and try if pump will work? Maybe there is broken wire somewhere on the way from foot microswitch to abs pump? I know brake light goes on after push pedal... Anyway it is not a big deal to try, and eventualy make bypass from switch to pump. What do you think? Thanks again

 

[Packer]

If the foot pedal works the brake light then the switch is working correctly. It is only a signal wire, it is normally a live circuit and when you press the brake pedal it brakes the circuit which triggers a relay to illuminate the light.

This normally works through the servo abs system but removal of the system frees up the blue relay which you can then utilise to operate the brake light.

One thought, if you open the bleed point on the servo system for the rear circuit and press the pedal does it eject fluid showing that the master cylinder is actually moving the fluid?

 

[roddy]

would it be worth checking the rear pistons move freely ?

As I was always under the impression that the servo systems had a degree of residual braking if the servo failed ?

 

[romek]

yes, master cylinder moving fluid for sure. Correct me if Im wrong. Just touching front lever (switch clicks, actually no pressure in system) makes light on and pump starts. If touching pedal gently, only light og, pump doest star. Maybe its electrical problem?

 

[romek]

would it be worth checking the rear pistons move freely ?

yes, freely ...

 

[Packer]

The light and the servo are controlled by the same signal wire connecting into the servo ABS unit. I'm not sure about this but if the light works and the servo doesn't it can only be an internal servo/abs fault. As the GS has linked brakes with the front lever working both front and rear brakes does your rear brake work when using the front lever? If not that makes it even more likely that the fault is with the servo/abs unit, probably the pump for the rear circuit.

 

[romek]

I'm afraid you are right So going down to cut servo. Wish me luck. Thanks for your time.

 

[Packer]

Try and get hold of a soldering iron and solder. It will make the jointing of wires much easier and more secure.

 

[(RIP) DitchWater]

Blimey,

That was interesting and well done to Packer for a day's worth of fault diagnosis. I'm glad I chose NOT to buy a bike with any additional form of braking assistance.

Just one thing to note: The soldering of automotive wiring is not recommended because it is fairly ductile and heating it will destroy it's elastic properties. The application of heat induces work hardening to the copper strands of the cable and is equivalent to hammering the wire 30 thousand times until it's temperature reaches that sufficient to allow the solder to flow.

If you're cutting and joining wires in the desert then a tight looped and foldback twist on a clean section of wire should be good enough, and don't forget to insulate it.

Enjoy your evening.

 

[romek]

Done. Everything works. Easy job Thanks for help and regards from Morocco - another happy biker without servo

 

[Packer]

Done. Everything works. Easy job Thanks for help and regards from Morocco - another happy biker without servo

Well done that man. You'll now be wondering why the hell BMW fitted the servo in the first place.

 

[Packer]

Blimey,

That was interesting and well done to Packer for a day's worth of fault diagnosis. I'm glad I chose NOT to buy a bike with any additional form of braking assistance.

Just one thing to note: The soldering of automotive wiring is not recommended because it is fairly ductile and heating it will destroy it's elastic properties. The application of heat induces work hardening to the copper strands of the cable and is equivalent to hammering the wire 30 thousand times until it's temperature reaches that sufficient to allow the solder to flow.

If you're cutting and joining wires in the desert then a tight looped and foldback twist on a clean section of wire should be good enough, and don't forget to insulate it.

Enjoy your evening.

Oh a big thanks for that DW, talk about ladling on the bad news When I removed my servo I was very careful to ensure that every joint was properly tinned and then soldered with good old fashioned tin/lead solder prior to insulating it. Now I can expect it to all fail due to work hardening, probably half way up the Dalton Highway surrounded by bears and clouds of man eating mosquito's. Thanks again.

 

[sockpuppet]

Glad to hear it.

 

[(RIP) DitchWater]

Oh a big thanks for that DW, talk about ladling on the bad news When I removed my servo I was very careful to ensure that every joint was properly tinned and then soldered with good old fashioned tin/lead solder prior to insulating it. Now I can expect it to all fail due to work hardening, probably half way up the Dalton Highway surrounded by bears and clouds of man eating mosquito's. Thanks again.

Sorry about that.

That's why nearly all automotive connectors have calibrated crimped terminals into connector housings. You may find some soldered common grounds, or earth's if you prefer, within rigid areas of the machine.

If the soldered cables are not moving they should be okay but if they flex they may fracture because the copper will now be brittle after the application of heat.

HTH.