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Brake failure light & flucuating speedo

6K views 19 replies 8 participants last post by  Robert_W 
#1 ·
It's been out of the shop for about 3 days now and this morning about half way through my 40 mile commute, the brake failure light starts flashing and the little red triangle is glowing bright red. Then I notice the speedometer drop to about 10mph and bounce back up to speed. About 3/4 of the way in, the speedo quits altogether (brake failure is still flashing). I tested the brakes and they work fine. The front is normal, but the rear seems to take a little more pressure. I don't use the rear a lot, so I'm not sure if I'm imagining that or not. I get about 5 miles from the office and the speedo decides to work again, but the brake light is still flashing. Any thoughts?
 
#2 ·
Well the brake failure could just be coincidence or maybe they pulled / pinched the wire a bit too hard while they had it in the shop and now it's the dreaded brake failure light. That should be a simple fix. But the speedo thing....hmm. Sounds like a loose connection. In fact, it all sounds like loose connections some where. Let us know when you find out.
 
#3 ·
dwsdad said:
It's been out of the shop for about 3 days now and this morning about half way through my 40 mile commute, the brake failure light starts flashing and the little red triangle is glowing bright red. Then I notice the speedometer drop to about 10mph and bounce back up to speed. About 3/4 of the way in, the speedo quits altogether (brake failure is still flashing). I tested the brakes and they work fine. The front is normal, but the rear seems to take a little more pressure. I don't use the rear a lot, so I'm not sure if I'm imagining that or not. I get about 5 miles from the office and the speedo decides to work again, but the brake light is still flashing. Any thoughts?
This is wild speculation on my part, but maybe the ABS sensor isn't working correctly.

Where does the speedometer get its information about wheel speed? The ABS sensor??

To repeat, this is just a completely wild guess with no real experience. But it may explain both symptoms.
 
#5 ·
I called Lone Star BMW and described what was happening. They suggested checking the speed sensor. I noticed more on the way home that does kinda point to the speed sensor:

- no speedometer
- no odometer or trip meter
- no cruise (will not set)
- self canceling turn signals won't self cancel
- brake failure light and triangle flashing

I'll check the wiring on the front wheel this weekend. I suspect a broken or pinched wire.
 
#9 ·
dpancerz said:
I agree with Chuck as the final drive comment makes no sense unless it was an attempt at levity.
It was both an attempt at humor, and slightly serious...

My 2 failures both were noticed by me from speedo issues.

I would pull the sensor out and see if there are metal shavings stuck to it.

Otherwise it still sounds like a sensor failure, wether it be a borken wire or the sensor itself. That is were all the inputs for the ABS, speedo, and even blinker auto-cancel come from that sensor.

But before pulling a bunch of panels, I'd pull the sensor and check for metal.
 
#11 ·
There are two speed sensors, one on each wheel. They are used for the ABS as well as the optional ASC feature, among other things.

I have pulled the rear sensor out on my 2007 K1200GT during a final drive oil change. The BMW repair manual (RepRom) gives a lot of warnings to be careful about how the wire is routed around the rotor (disk), calipers, etc. Clearances are very tight, and tugging on the wire could break it in a way that would not be easily seen.

Before pulling out the rear wheel sensor, you might want to do a quick visual inspection of its wire first. Perhaps you will see something obvious, where the wire wasn't properly routed around all those components.

If you decide to pull the rear wheel sensor to inspect it for metal fragments, you won't have to worry about final drive oil leakage - the normal oil level is below the sensor. You may want to have an extra gasket on hand (a cheap part) in case you nick the old one. Work slowly and carefully. It is a relatively easy job.
 
#14 ·
Brake failure light & flucuating speedo - UPDATE

Well, after looking up the price of a new speed sensor and verifying that the extended warranty would cover anything electrical or mechanical, I decided to take the bike over to Shreveport Motorsports.

I got a call from them yesterday telling me they pulled the rear wheel sensor and found metal bits all over it. They cleaned it off and started the bike. The good news is, that fixed the blinky brake failure light and speedo. The bad news is that when they spun the wheel it quit working again, and after pulling the sensor again they found more metal. :|

The tech said that the fluid in the unit looked really nasty like it hadn't been changed in a long time. Well, that just ain't the case. I told them it was serviced in Jan and only has about 3K on the change. BTW, Alamo BMW in San Antonio did the service work in Jan. Stay far, far away from those clowns!

The service manager said that if I had proof that it had been changed, it would be easier to fight the extended warranty folks to get them to replace the final drive (if indeed it is bad), so I went home and found the receipt from Alamo. Sure enough, it's dated 1/5/2011 and the mileage was clocked in at right at 60K. I'm faxing that over to Shreveport this morning.

More as it develops...........
 
#16 ·
Interstate STAR has requested that the shop call me for authorization to tear down the drive unit to determine the cause and damage. Here we go...............
 
#17 ·
Trust but verify....they might have changed the oil. If your FD was on it's way out the door in the first place 3,000 + miles on it could certainly trash your oil. Either way it sucks. Hopefully the warranty company will step up and not fight you. Let us know.
 
#19 ·
I talked to Shreveport Motorsports this weekend. The warranty folks approved the replacement of the final drive without even coming out to view the drive. The tech said the oil was black with lots of metal bits in it. The gears showed wear, but not that much. The bearing was completely destroyed. The fact that I had proof of the fluid being changed around 3K miles ago saved my bacon on getting Interstate STAR to cover it. While it's in there, they're replacing the rear brake pads.

All I'll be out on this is the cost of the brake pads and installation time. Interstate STAR is picking the entire tab on the final drive.
 
#20 ·
Cool beans man....glad they didn't hassle you. Some times these extended warranties are worth it.
 
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