ABS Brakes (again I am assuming)

[Hunda67]

Hi,

New here but couldn't find the exact symptoms I'm getting so thought I'd just ask

I have a 2006 R1200GSA - I have had it from new and has suffered a lack of use the last few years but now using it again more. Yesterday the brake failure lamp was flashing after a 20 mile ride - all was OK when I set off. I switched off ignition and started the bike again and all was OK a few yards after setting off as is normal. I left it for a while and next time I turned the ignition on the brake failure was flashing faster than usual. Without starting the engine pulling the front brake lever did nothing - i.e. no servo motor running as you usually get. Pressing rear brake and the servo motor started and didn't stop when releasing lever until ignition turned off. It seems to have settled into this state of affairs now - back brake causes servo to run continuously and front brake doesn't start servo. I have checked the levers (nothing fouling on handguard or anything) and I have checked the microswitches at the levers and both seem to be working cleanly. The battery is new and there are 12.7V across the terminals with ignition on. Any help appreciated on what to start checking next and where to look.

Thanks for any assistance given.

 

[patzx12]

Use a meter to check the micro switches. Remember they ane -- NORMALLY ON -- configuation

 

[Bear]

Check the adjustment of the brake switches. You should hear each one click as you operate the brake. Last time I had this sort of problem the alloy front lever had worn a couple of thou so the microswitch operated as if the lever was being pulled. There's a tiny allen screw under the lever: slacken it off and adjust the position of the switch until it clicks when operated. It needs careful adjustment as you want the servo to start as soon as you pull the lever.

 

[Hunda67]

Thanks. The switches are fine - no change until I pull or press the lever and then they act fine - so seems the problem is maybe deeper - where should I go off hunting next?

 

[Simon-GS]

I think a GS911 is your friend here. I know its a lot of money but I was really impressed with mine and diagnosed my brake fault in a matter of moment. Plus will be useful for servicing in the future.

 

[Hunda67]

I've thought about it but as you say quite expensive and not sure it would be used that much. How much detail can a GS-911 go into about the braking system - will it pinpoint the exact area of the fault mostly?

 

[Bendy toy]

Like any other ECU code reader, the 911 wont always see an actual fault, but the hidden symptoms it does find will lead you to discovering the actual fault.

 

[Hunda67]

Still trying to avoid splashing out.

I had a further investigation this evening after bike hadn't been touched for 24 hours. When I went out and switched on ignition all behaved normally (turn on ignition, goes through startup sequence with a quick buzz of the servo) so drove it a few yards and all worked as normal - brake warning light went out. Switched off ignition and repeated a few times and always good. So took it for a ride and after about half a mile brake warning started flashing but servos still working. Turned round, stopped and switched off. Started all again and everything normal until about half way back home and brake warning flashing again and this time servos not working. Rode it home and sometimes with ignition on front brake no servo and rear brake servo sticks on. Other times front brake servo works but back brake servo always stays on until ignition switched off. Brake warning light always flashing fast.

I rechecked battery, switches, tail light and wiring (as far as under seat), front and rear brake fluid levels, brake pads - all OK.

I'm guessing as brake warning always flashing fast without the bike moving it can't be the wheel sensors. It is also strange the symptons change and it sometimes works OK for a short distance if the bike is left a while. So was wondering if the intermittent symptoms indicate something stupid or something more expensive?

 

[Simon-GS]

On mine, the GS911 showed the motor as open circuit, so i knew it was the ABS unit at fault (could have been wiring I supose) also once i fixed it I was able to exercise the motor a few times using the GS911 to check the fix was good. First time I fixed it i put it back together and exercised the motor a few times, it worked 4 out of 5 times but failed every now and then. Took the motor apart again, cleaned and opened up the brush holders a little more and it then passed 5 out of 5 tests and has been good since.

You can also exercise valves in the ABS unit itself to check their functioning correctly.

 

[Hunda67]

So is the ABS unit accessible and repairable then? I thought they were a sealed unit? I certainly don't want to be paying £1500+ for a new one so am just trying to exhaust all possibilites.

 

[Simon-GS]

Have a search on the net, plenty of videos and pictorial tutorials. Yours may have different ABS to mine (I have non servo ABS) I removed the tank and bodywork, removed the motor from the ABS unit, fixed it then replaced it all. Its fiddly to get off but I managed it without removing the AS unit from the bike. if you don't fancy doing it yourself I have seen companies advertising repairs (in the UK) for a few hundred pounds. This will mean removing the whole unit from the bike and refitting/bleeding etc.

Without knowing if it really is the ABS motor you could be wasting time/money in repairing it only to find you still have the same issue! Only an engine diagnostic tester can tell you this with any degree of certainty.

 

[Hunda67]

Ok thanks. Sounds like a gamble. Splash out on the tester or take it somewhere - trouble is I live in Shetland and nearest BMW dealer is 12 hour ferry crossing to Aberdeen away.

Mine has servo's - but I'm guessing it is all part of the ABS system - but it will be different from your bike. I'll maybe delve deeper and see what I can find before spending the money but open to any advice from anyone who has the same bike (2006 R1200GSA).

 

[Steptoe]

On mine, the GS911 showed the motor as open circuit, so i knew it was the ABS unit at fault (could have been wiring I supose) also once i fixed it I was able to exercise the motor a few times using the GS911 to check the fix was good. First time I fixed it i put it back together and exercised the motor a few times, it worked 4 out of 5 times but failed every now and then. Took the motor apart again, cleaned and opened up the brush holders a little more and it then passed 5 out of 5 tests and has been good since.

You can also exercise valves in the ABS unit itself to check their functioning correctly.

His bike is a servo/abs, completely different system and problem to your version, which is just ABS with no servo brake assist..

Ok thanks. Sounds like a gamble. Splash out on the tester or take it somewhere - trouble is I live in Shetland and nearest BMW dealer is 12 hour ferry crossing to Aberdeen away.

Mine has servo's - but I'm guessing it is all part of the ABS system - but it will be different from your bike. I'll maybe delve deeper and see what I can find before spending the money but open to any advice from anyone who has the same bike (2006 R1200GSA).

You really need the fault codes read.
Any advice offered would be pure guess work and no help whatsoever.

The GS911 can tell you the actual pressures in the front and rear brake system and if they're too high or too low and let you know what the problem is. .

 

[Hunda67]

Thanks. Looks like I need to either buy a GS-911 or find someone in Shetland who has one (I'll ask around but not many GS's up here). I then guess depending on what the problem turns out to be. If it needs a new ABS pump I don't think I can justify the cost for a 10 year old bike but it's also only done 17k miles! If it does turn out to be that expensive I guess it's a case of remove ABS and Servo's - would that make my braking like the wooden weak brakes you get when you first set off or would it be improved?

 

[Bendy toy]

What is the cost of a new bike to replace the now almost worthless bike with broken ABS?

Factor that in and the repair wont seem so pointless even though the cost might still be eye wateringly high.

 

[crawling finn]

Could it be simply just low brake fluid level? That is in the reservoirs on the servo.

 

[Hunda67]

Yes cost of replacing bike is in my thoughts - as you say nearly worthless in that state but since I've had it since new and its only got 17k on the clock, its still nearly new as far as I'm concerned (it's been well looked after) and as I don't do the mileage I used to I can't justify replacing it (which I can't afford to do these days ).

I'm still hoping it can be something as simple as low brake fluid in the servo resevoirs - I haven't got that far yet. Tonight I removed the rear brake pads and checked the pistons are sliding smoothly which they are and also took the rear sensor out and cleaned the swarf on it. Again tonight things seemed to work correctly initially and then it went back to front brake giving no servo noise and rear brake causing servo motor to continuously run. However, I did discover (when pumping rear brake after refitting caliper) that the rear servo stops if I press the rear brake fully hard on for a few seconds - I don't know if this indicates something like low fluid in the servo resevoirs?

I'll start with dismantling the tank to get to them tomorrow or over the weekend when I get the chance.

 

[Deleted account 181015003]

There is a GS911 for sale on here you could buy it use it to help sort you bike and resell it without too much of a loss

You need to subscribe to see the for sale section of the website

 

[Steptoe]

Thanks. Looks like I need to either buy a GS-911 or find someone in Shetland who has one (I'll ask around but not many GS's up here). I then guess depending on what the problem turns out to be. If it needs a new ABS pump I don't think I can justify the cost for a 10 year old bike but it's also only done 17k miles! If it does turn out to be that expensive I guess it's a case of remove ABS and Servo's - would that make my braking like the wooden weak brakes you get when you first set off or would it be improved?

. Mileage is irrelevant to the servo failing. I've abs/servo modulators I've removed as low as 14k miles. The brakes you'll have are not like the residual braking you have when the servo isn't working - the brakes you'll have if you remove the servo are the same brakes and braking power as fitted to post 2007 bikes.

Could it be simply just low brake fluid level? That is in the reservoirs on the servo.

Low fluid level shows as a solid red light with no flashing, plus if the fluid in the servo modulator are low the brakes still work as normal .

 

[Pukmeister]

Your rear brake servo cuts out when the rear brake pedal is held down. This is a normal feature on ServoABS models to prevent battery drain from servo operation during hill starts etc. It will give a kick every 30 seconds or so as it pulses the Servo to boost/restore rear brake line hydraulic pressure.

Conversely the front brake should keep the Servos running permanently when front brake lever is held as a design feature. I have no idea why BMW designed the system this way.

The simple checks are brake switches, battery charge state and brake fluid levels in both the master cylinder reservoirs and the Servo units integral reservoirs on the ServoABS pump beneath the fuel tank. A tired battery can throw up ABS faults. If your brake pads are well worn the servo reservoir levels will probably be low. Simply fitting a new set of pads can sometimes cure this. Filling the servo unit then replacing worn pads can result in an overfilled ServoABS unit (as the displaced fluid with fitting new pads has to go somewhere.)

As Steptoe says, you need to read the fault codes to know what is actually wrong. Without a GS911 or dealer diagnostic kit you are just guessing or hoping to strike lucky.