2002 R1150RT Rear Master Cylinder?

[jon989]

I just purchased a 2002 R1150RT (16,500 miles on it) and decided to address what I saw as the major issues right off the bat. I also wanted to reset the maintenance schedule as the previous owner wasn't volunteering much information. My issue arose after replacing the brake lines. Installation and bleeding went well with the front (so far... as I've not road tested it); however, the rear has issues. Initially, the rear master cylinder was pumping OK. While bleeding the back, the fluid that came out of the ABS unit had the look of Vaseline (looked funny and might have been a little thicker than usual). During the bleeding, the fluid stopped pumping from the peddle. With power on, the front brakes work and will activate the rear brakes (iABS working properly). When the rear peddle is used, the brakes don't work. I'm guessing there is a blockage after the reservoir up to the master cylinder or the master cylinder decided to give out. Any thoughts before I start on a new mess? Any history on the rear getting clogged or the rear master cylinder going bad? Again, it appears the issue is upstream of the ABS unit.

New member and first question. Thanks for the help I've gotten reading your replies to others issues.

 

[kioolt]

Does the servo pump start when you press the brake pedal? If not, check the brake switch.

 

[jon989]

The servo comes on (switch works); however, there is no resistance on the brake peddle through its full motion and it does not engage the brakes.

 

[AntonLargiader]

You realize there are four reservoirs on this system, right? That the reservoir under the seat isn't the fluid that comes out at the caliper? I'm not trying to offend you but this is something that not everyone realizes. Confirm, and we will take it from there.

 

[jon989]

Yes. All four filled. I used the video from Beemer Boneyard as my "How to" guide.

 

[QSrider]

There are reports of OEM black rubber line breaking down on the inside and little bits of soft rubber clogging things up. If your brake lines are original ones, they are getting up there in age and might need replacing.

This is what I'm talking about:



Good luck!

 

[gsaddict]

If you still have the Black rubber original brake lines......

Even if the lines appear ok replace them asap with SS Teflon ones.
They ALL fail and will either burst or mess up the brake circuits & ABS pump.
Do it now.

 

[ragtoplvr]

He said he was replacing the brake lines. First, which side is not bleeding, the brake pedal side or the side from the pump to the caliper. Which bleeder screw does the strange brake fluid come out of. It appears there is a air bubble or something somewhere. The thick fluid thing concerns me. That would need flushed.

Rod

 

[AntonLargiader]

You just have hard pipe from the rear MC to the ABS unit, right? I would remove that at each end and see it if is clear (blow it out) and then remove and disassemble the rear MC. Yes, they do go bad. I replaced one about three weeks ago. Could easily be that operating it full stroke after it hadn't been maintained well killed it.

 

[jon989]

Rod is correct. I was replacing the lines when this happened. The problem is on the pedal side. I'm thinking the next step it to divide and conquer (check for blockage, flushing, checking master cylinder) unless there are any known issues on this side of the brake circuit that any of you have seen.

Jon

 

[jon989]

Thanks Anton. I think that is the next step. Will give it a shot after work today.

 

[jon989]

Thanks for the help. Was able to get a used master cylinder and flushed everything out. The fluid that came out was pretty bad looking and there was some black chunks of crud that flushed out. Based on how well things are working and how much better the brakes are working (and feel), the old lines had to have been blocked. There were a couple of bone head mistakes on my part during the troubleshooting, but I guess that is par for the course.

Again, thanks for the help.