Brake light staying on/servo issues

[JDARLINGTON156115]

Folks,
Hoping I can get some help.
Yesterday, about 4 hrs. into a 6 hour tour, my son who was following on his bike told me my brake light was staying on.
We decided to head for the barn as we still had about a 2 hour ride to get there.
The brake light continued to be more on than off and I was very conscious of making sure I wasn't inadvertently touching either one.
Less than a mile from home we stopped to pick up some groceries.
When I got back on the 1150Rt I had no working power servo and was reduced to the residual brake function. My god, I'm glad I only had a short distance to cover.
Once bike was on center stand I checked my brake fluid level for front brake and noticed it was closer to the center dot ,below the upper line minimum recommended level.
I'd prefer to top it off with BMW brake fluid but don't have access to any.
Wondering if it's a mistake to use a non BMW DOT 4 product to top it off.
Am hoping that whatevers going on is related to this and not something more serious.
If anyone else has experienced something like this please weigh in with your experience,outcome and advice.
I purchased the 2004 1150Rt six months ago with 5,800 miles. I've put about 2,300 miles since then. Bike had it's 6,000 mile service at a BMW dealer I'm hoping with the recommended brake flush. The bike has always been stored by prior owner and me in a conditioned garage.
This has me more than a little spooked .
Thanking any one in advance for any help or incite which might be helpful.
JFD

[mpmarty]

Either Dot 4 or Dot 5.1 should be fine. BMW doesn't make brake fluid, they buy it just like you or I. DO NOT USE DOT 5 fluid it is not for your system. Dot 5.1 is OK but I'd stick to just plain Dot 4 to be safe. I doubt filling the reservoir on the handlebar will solve your problem. Might be time to remove the tank and take a look at the fluid levels in the control unit. If you have access to a GS-911 you might try to read the fault codes. Good luck with your RT. I had an 04 RT and it was a superb bike in every respect. Awesome brakes.

[Pauls1150]

Hi J,
Yeah, those "residual" brakes are a [freakin'] joke for a bike of this weight & power, pretty scary the first few times you hit 'em. Pumping helps - if you have the time & presence of mind...
Make Darn Sure - at the shop that did the 6K service - that they actually flushed out the ABS control unit, AND that afterwards, they put it on the computer to Verify that it actually built up the hydraulic pressure in all circuits. If it was done, they should be able to show you the record. "What record?" or "We don't save those" means it wasn't done. (A GS911 can't give you those numbers.)
Any ol' DOT 4 fluid is fine (it's a federal specification); preferably from a freshly opened container so it hasn't already absorbed some water from the local ambient.
Possibilities are - there may still be a little air bubble in there: flushing the ABS control can be a real PITA, and only a shop has the official BMW computer to measure the actual brake pressure; there may be a bit of dirt clogging a port; or there may be an electrical fault in the ABS. If any of the ABS lights are blinking, pull fuse #5 and reinsert after 20-30 seconds to reset it.
A MityVac garage bleeder may not be not sufficient for the ABS unit.
And keep the battery on a "smart" trickle charger; the ABS pulls a lot of current.

[DrPaul]

Once bike was on center stand I checked my brake fluid level for front brake and noticed it was closer to the center dot ,below the upper line minimum recommended level.
I'd prefer to top it off with BMW brake fluid but don't have access to any.
Wondering if it's a mistake to use a non BMW DOT 4 product to top it off.
Am hoping that whatevers going on is related to this and not something more serious.JFD

You have adequate brake fluid in the front MC reservoir. I don't think that's the problem. Are you getting any "Brake Failure" or /!\ warning lights?

[flars]

Fluid has nothing to do with your problem, which is the brake light staying on.
If the ABS senses the brakes are on when you turn on the ignition (and the brake light being on kind of suggests to the brain that the brakes are on), the ABS will not initialize, which will result in residual braking only.
The usual suspects are:
a small stone or something in the rear brake pedal;
crud building up around the front brake lever, which does not permit the brake light switch, which is operated by the brake lever to return to its 'off' position;
a chafed wire going to the rear brake light.

Examine up under the front brake reservoir to see if there is any sign of green or white gunk. You may have to pull the rubber boot that covers the grub screw that the brake lever pushes on to be sure you don't have junk under there.
Look at the rear brake light wire.
Check for junk around the front brake light switch that is preventing the switch from deactivating.

[acejones]

If you have handguards I would check to see that the brake lever is not contacting the handguard. They can get out of position, and not allow full travel of the brake leveI. (to the off position).

As for your question about BMW brake fluid, as a previous poster said, BMW doesn't make brake fluid, nor do they make oil, batteries, etc. The stuff that has BMW stamped on it isn't magic.

[JDARLINGTON156115]

Lars,
Appreciate the feedback. Your comments make a lot of sense. I'm hoping that's the problem.
JFD

[devauxb]

There are two small 'micro switches', one at the front brake lever and one at the rear brake pedal that occasionally get hung up due to dirt/corrosion, ... If you are lucky you can clean them up, relube them and you are good to go. Sometimes you may have to replace them.

When working correctly if you depress either brake, you can hear a faint 'click' - that is the switch doing its thing. Good luck!

[themayer]

Fluid has nothing to do with your problem, which is the brake light staying on.
If the ABS senses the brakes are on when you turn on the ignition (and the brake light being on kind of suggests to the brain that the brakes are on), the ABS will not initialize, which will result in residual braking only.
The usual suspects are:
a small stone or something in the rear brake pedal;
crud building up around the front brake lever, which does not permit the brake light switch, which is operated by the brake lever to return to its 'off' position;
a chafed wire going to the rear brake light.

What flars said. I had exactly the same problem, except I was on top of the Beartooth Pass on my '04 RT! Pretty scary trying to get down from there with only "residual braking". When I got down and got to some cell phone service, called my mechanic back in California. He told me that a problem with the brakes not booting up is ALMOST ALWAYS caused by the servo-assist brake system reading the brakes as ON when the engine is started. I finally determined that the rear brake pedal wasn't coming all the way back up after I used it. Adjusting it didn't help, so I quit using it until I stopped for the night and had time to just sit on the ground next to the bike and think about it. Eventually found a small stone wedged between the lever linkage and the side case. Stone out--problem solved. Good luck. Let us know the outcome.

[Pauls1150]

Crud or debris around the linkage or switches - didn't even occur to me, but that's the first thing to check! Darn... Always do the easiest things first.

Does anybody actually make handguards that will fit the RT??? I'd love to reduce the rain on the gloves (don't need to do any "bark-busting"), but our handlebars are an unusual size and shape...

Thanks,

Paul S

[aerialfilm1]

I'm having the same problem only mine was working fine until I did the control circuits flush. When I headed to the wheel circuits the servo wouldn't engage to draw the new fluid through the mini-stan. Brake Failure light stays on and no rear brake light on either lever.

02 RT has 42k and so far has not suffered any of the typical issues this year is know for. Maybe my luck finally ran out. In the morning I'll look for interference with the brake levers. Any other suggestions appreciated.