Author Topic: R1150RT 2002 i-ABS strange behavior  (Read 7201 times)

14TLC

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R1150RT 2002 i-ABS strange behavior
« on: June 01, 2016, 12:16:44 PM »
Hello. I'm new to this forum and I find to be very useful since most of the members relate the bike issues with the errors getting from GS-911. Although I'm using different diag sw/hw and still don't own GS-911 (considering to buy the pro version in near future) the error codes are the same.

So, here is the story and the issues. I'm servicing my friends bike, R1150RT 2002, which he recently bought. The bike has been very badly maintained, although the previous owner was always servicing the bike at official BMW dealers.
The bike had error codes for low brake fluid level and low pressure in the front wheel circuit. The brake fluid in both front control and wheel circuits was in bad condition, pitch black color but fortunately without sludge or residues in the the reservoirs. The rear circuits were not properly bled and had air in them. After changing brake pads, brake fluid and bleeding as per BMW service manual the fault codes are not present any more and there is massive improvement in braking. But there are 2 issues that are bothering me and I appreciate your opinions :

1. On some occasions the GEN light will turn on with ABS light off. The GEN light stays on until I turn off/on the bike. The strange thing is that there are no error codes stored in the DME/ABS. Both the brake and tail bulbs are working. Just for test I removed the bulbs and the DME/ABS reports the errors for both lights. I also tested the brake lever switches. Both of them working and properly report their state to the DME/ABS. Just for test, I was holding the brake lever switches while operating the brake levers and than the GEN light turned on and there was an error in the DME/ABS indicating that the hydraulic brake was activated before the brake lever switch.

2. The second issue worries me more. In normal braking conditions the brakes and servo are working very well, but if I pull the the brake lever very hard, past the usual brake lever travel, the servo pump changes the usual noise to more louder and higher frequency noise and the GEN light will turn on with ABS light flashing fast (4Hz). When I release the brake lever both lights will turn off. Did not notice any compromised braking. Again the strange thing is that there are no errors in the DME/ABS. This also happens when the engine is not running and I'm slowly pulling the front brake lever past the usual lever.
The normal pressure in all control and wheel circuits are around 20-22 bar. When brake levers are operated without the servo running, the pressure difference between the control circuit and wheel circuit is around 6 bar (21 control, 27 wheel). But when the servo is running and pull the front brake lever to the point when the GEN light turns on and ABS flashing at 4Hz, the pressure in the rear wheel rises up to 87 bar while the pressure in the front wheel circuit goes up to 35 bar . This happens no matter whether the front or the rear brake lever is operated, although it needs more force on the rear brake lever to come to this state.
I also tested the control valves and they report correct functioning.

I appreciate your thoughts and opinions