Another ABS problem

[ManxGS]

Good evening everyone. This is my first post so go easy on me. I've a beautiful 2004 R1200GS with only 2700 miles on her. She sat for 10 years in a dry garage and apart from dust wanting cleaning of her she's showroom.  New battery and a service and we're off. 250 miles later and I have to leave her outside overnight, it rains and when I go to start her the next day, ABS failure, warning triangle, and no servo on the rear circuit.  911 reads 1 code present. 
24972 Pressure in rear wheel circuit too high.   when I read live data, battery 12.36v, pressure front circuit 18.17bar, rear circuit 47.11bar, and when I press both levers front operates motor but rear does not, and the live data says front not operating and rear is??   weird.
Any help will be greatly appreciated.

[Alexm1]

ManxGS, the first thing to try would be a full brake system bleed, both wheel circuits and control circuit. The fluid will likely be quite contaminated so you need to ensure the system is fully flushed.
Probably not contributing to your problem but worth thinking about is the OEM brake lines, they are likely soft and replacing them with braided lines will improve the brakes performance.

[ManxGS]

OK. Fluid all changed and no nasty's found. Same problem persists. What I can't understand it the pressures recorded on live data with all the nipples loose. Front 18bar, rear 62bar. Also the data shows that the front switch isn't working yet the light and motor runs, and the rear switch does work yet the motor does not run.  Should there be any pressure reading when idle??

[Alexm1]

I am missing something here, "all nipples loose", do you mean open? And you are still getting pressure readings?
Check the switches physically and electrically if you are able, get them out of the equation.
What colour was the control circuit "old" fluid?
Have you performed the brake pressure test?

[ManxGS]

Yep. All nipples open, all of them just incase there was some trapped pressure in the circuit somewhere. How do I test the pressure sensors? are they inside the ABS block or outside on the circuit somewhere? The fluid looked like fresh out of the bottle.

[Ghiribizzo]

Inside the abs block. As Alexm1 said - have you tried the bleed test on GS911? What did it say?
I'd expect a problem as you normally need to press very hard on the pedal to get the pressure up and hold to see if it maintains it.
But if the 'apparent' fault is over pressure (even if there isn't any in reality...) then the pump wont run and well - i *think* you would not be able to complete the bleed test.
Keep us posted.


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[Ghiribizzo]

I also wondered about brake lines. Ive changed plenty originals where they ballooned up - hoses coming apart internally. They can also fail where they wont release built up pressure. But you were able to get fluid through the rear wheel circuit?


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[Old goat]

Hello ManxGS
I hate to be the bearer of bad tidings, but your symptoms are exactly the same as I had on my 2005 R1200RT with the same electrically-assisted  iABS-1 system. I could not resolve it by any amount of flushing and clearing fault codes and I learnt that what I had was typical of a failure of the ABS unit, presumably of the rear brake pressure sensor though that was never made perfectly clear. The unit is not serviceable: BMW do not supply parts and there seems to be no one (in the UK at least) able to overhaul them. BMW abandoned this system after 3 years (I think) and so the bikes with it are now old and interest must be waning. Faced with the absurdly high cost of a new unit I had the ABS system removed so that the bike now has conventional non-assisted braking. I much prefer the brakes now. They are just as powerful but without the grabby operation of the assisted operation. It was done by Sherlocks and the result is that everything still works (speedometer, self-cancelling of direction indicators ...) and there are no brake warning messages, but there is course no ABS. You also lose the warning triangle in the instrument panel. The ABS unit (separated from the hydraulic parts) is retained and will reveal fault codes to a GS911, but these no longer matter. The cost on my bike was less than £450 – I think it varies a bit according to model. They did it in the day and lent me a bike while it was in.
The alternative approach is second hand unit, but it will be expensive and there will always be the fear of another failure.
Good luck

[ManxGS]

Inside the abs block. As Alexm1 said - have you tried the bleed test on GS911? What did it say?
I'd expect a problem as you normally need to press very hard on the pedal to get the pressure up and hold to see if it maintains it.
But if the 'apparent' fault is over pressure (even if there isn't any in reality...) then the pump wont run and well - i *think* you would not be able to complete the bleed test.
Keep us posted.


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Forgive my ignorance, and I've looked it up, but how do I perform a bleed test via GS-911? Cant find anything specific on the menus. I am beginning to think its defiantly electronic rather than mechanical. I did suffer a low battery problem last week and I tried to start without success. Hence the new battery. Came to work on the bike tonight and low and behold when I turned on the ignition both motors in the ABS unit ran, you can hear a definite twin motor note when all is fine during its self test. Leaned over and pressed the rear lever, motor ran. Hooray I cried. Plugged in the 911 and readings were nominal. 5 mins later all bad again. Spent all night then re-bleeding testing micro switches wiring and so forth. I'm done in.

[Ghiribizzo]

I'll get back to you tomorrow. GS911 is not 'here'...
When you say you were re-bleeding - can I ask how you did it?


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[ManxGS]

Just the best I can do with bleeding it manually via the levers, as the rear circuit motor won't run it's a little tricky but the front runs so primes up fine.

[Alexm1]

ManxGS, I suspect you are not following the procedure for bleeding Abs brakes. The is a good write up on the ibmw site. Suggest you get it and try again.

[ManxGS]

I'm certain I'm not following procedure Alex, I've no motor to run up the rear circuit, but the front is running and bleeding fine. I've a known good ABS unit coming tonight to try, so I'll update with the results of that test.

[Ghiribizzo]

Sorry i was busy - didnt get back to you... did you try the brake pressure test on GS911?


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[ManxGS]

I didn't my friend. No obvious option on my GS-911