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Low Level Brake Fluid Warning due to worn pads?


Mike O

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What indications are there of a low level brake fluid warning on an early 2003 R1150RT?

 

Seems I read somewhere that early 2003 were more susceptible to low level brake fluid as the brake pads wore.

 

Or am I wrong?

 

Mike O

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What indications are there of a low level brake fluid warning on an early 2003 R1150RT?

 

Seems I read somewhere that early 2003 were more susceptible to low level brake fluid as the brake pads wore.

 

Or am I wrong?

 

Mike O

 

Mike on the EVO brake system there should be plenty of brake fluid in the controller to handle normal brake pad wear.. If you run low on fluid (the fluid that goes to the brake calipers is contained in the brake controller under the fuel tank) the dash brake warning light should come on..

 

If you decide to add more fluid be sure to remove the extra fluid before re-padding the brakes as the extra will push back & out when the brake caliper pistons are pushed in..

 

Twisty

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Thanks Bill...

 

I did some more searching and found this quote from Jamie:

 

I usually time my pad swaps with annual brake bleeds to avoid the low level warning. This is especially important in the pre-late 2003's and the front wheel circuit reservoir holds much less fluid. They increased the holding capacity of the front reservoir in the later models to help avoid this problem.
(my emphasis)

 

It's in this thread with respect to Leslie's brake bleed.

 

What kind of 'warning' do you get?

 

Mike O

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I don't know which specific combination of solid/flashing red lights you get if the level drops enough to trigger the warning, but when BMW changed the wheel circuit reservoirs from those needing the original "Mini-Stan" design to the deeper threaded one (with the vents on the side of the cap instead of coming off the top, sometime in mid-late '03 model year) they also made the front wheel circuit reservoir larger. This can be seen in a few pics here from people posting doing their own bleeds on the later model bikes--the front reservoir is about an inch taller than the rear. There are eight pistons on the front wheel circuit to take up fluid from the reservoir as the pads wear and the pistons move towards the rotor. There are only two pistons in the rear so that reservoir drops only 1/4 as fast. Evidently, BMW figured out that they needed more reserve(oir) of brake fluid to be assured of keeping the intake to the servo pump covered--especially in the case of a tip-over with either control input being activated (lever or pedal). I believe you will also get a warning if the servo sucks in enough air to fail the start-up test, but again I don't know which variety/combination of warning lights as BMW doesn't make that info readily available to the non-initiated and I don't have the $70,000 computer. I've only experienced the low fluid level once at the SoCal Tech Daze when a K-bike rider forgot to top-up one of the reservoirs after a bleed, but I don't know what pattern of lights/flashing he got.

 

I would say, if you've got ANY lights on after you start and ride the bike down the driveway you should look into it. For reference, our two early model EVO's give:

 

Key on: red triangle with exclamation point (general warning light) steady on; "brake failure" light stutters (with clicking under tank) for a half a second, then rapid flash until servo start-up (quick high pitched whine) for another second, then slow flash until bike is started, warning light goes out a second after "brake failure" light goes to slow flash (before starting). If your bike doesn't follow that pattern or if the warning light stays on (before or after you start the bike), you've got something amiss. If you've got a lot of miles on your last bleed and haven't changed pads, one quick diagnostic would be to pull the calipers, push in the pistons a bit and shim them in place, then try the start-up sequence and if the light pattern you were getting was indeed a low fluid level and it now goes away, you've got your answer! thumbsup.gif

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Thanks Jamie...

 

Bike is due for a bleed. This is an intermittent (I hate those) indication that has appeared 3x in the last 1500 miles. Starts up and passes the initial test sequences just fine (it's an early 2003 like yours). Brakes operate just fine (servo and ABS function).

 

Then (out of the clear blue), I'll apply the brakes, glance down at the dash I'll get the two lites flashing at a 1hz rate; this is under and after normal braking. Brakes are still operating fine, I pull over, turn off and restart the bike and clears the indication. Won't see it again for 500 miles or so. Other than it occurs within a few miles of initial (from cold) operation, nothing else indicative of a pattern (my research shows the sensitive low battery issue that affects some ABS systems is a startup phenomenon - the behavior I'm seeing does not resemble that scenario)

 

These are the original pads (w/36k on the bike). Brake fluid reservoirs (front and rear) are fine. Have NOT checked under the tank. In any event, looks like I'll be minimally doing an inspection followed by replacement and bleed.

 

Any other thoughts?

 

Mike O

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Have NOT checked under the tank.

The two reservoirs on the ABS unit are the only two monitored for fluid level. While in theory there should have been enough fluid in each of them to accommodate the full wear range of pads, stuff happens and those reservoirs would be on the list to check.
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Officer_Impersonator

I've experienced the same phenomenon with my 02 RTP. I took it to my 'wrench and he topped off the brake fluid reservoirs and the problem went away. Then a couple of months later, the same brake failure lights came on again. I knew it wasn't from low brake fluid, so it must have been something else. Just for fun, I thought I'd put the bike back on the battery tender. (Since it's an RT-P, with a beefier alternator and two batteries, I figured I was done with my tender). Voila - keeping the battery topped off eliminated my brake failure lights from re-appearing.

 

Like you, I'd be riding along enjoying the ride. While the engine was at load and an RPM higher than idle, everything was fine. But when I'd stop at the end of a freeway off-ramp, occasionally the red lights would come on. Or, I'd be riding through my neighborhood, and just as I pulled into my garage, the lights would come on. It was the combination of low engine RPM (and thus low alternator output) combined with brake lights, running lights, headlights, etc. that ran the battery voltage down enough to trip the ABS system.

 

I've combed through your posts a couple of times trying to get a sense of your situation. I'm still not convinced that you're not experiencing the low voltage situation, even though you say it's not the low voltage situation.

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I've combed through your posts a couple of times trying to get a sense of your situation. I'm still not convinced that you're not experiencing the low voltage situation, even though you say it's not the low voltage situation.
Unless this is a new 'low voltage situation', every one that I've researched occurs at or about the moment you start the bike for the first time (when engine/started are cold and current draw is the greatest). Here's another quote from elsewhere on the board:

 

If with ignition on the lights flash together but go to alternate flashing when you start the engine, it means low voltage while cranking. Means low battery, tired starter motor, corroded connections... any of this. After riding a few minutes, if you stop, shut off and restart, it should be OK.
If I recall correctly, this is a test sequence at startup time that requires a minimum voltage be detected for the ABS to believe it will function properly. Failing that voltage test, it will produce the diagnostic code stated in the quote above. What I'm experiencing (and is similar in description to yours) is NOT occurring at startup but well after I'm underway. What I'm reading into your explanation would indicate a weak charging system or discharged battery would produce the same diagnostic indication well after you're on the road and riding. I've ridden with an almost dead battery and never had the brake lights illuminate.

 

Does anyone know if the ABS voltage requirement is tested beyond at bike start up time?

 

It's no wonder this is a bit difficult to diagnose. Imagine a week alternator (or slipping belt) causing your brake system to signal a brake failure.

 

Mike O

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Have NOT checked under the tank.

The two reservoirs on the ABS unit are the only two monitored for fluid level. While in theory there should have been enough fluid in each of them to accommodate the full wear range of pads, stuff happens and those reservoirs would be on the list to check.
Yup...I'll be checking that, too. Thanks Ken.

 

Mike O

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Thanks Jamie...

 

Bike is due for a bleed. This is an intermittent (I hate those) indication that has appeared 3x in the last 1500 miles. Starts up and passes the initial test sequences just fine (it's an early 2003 like yours). Brakes operate just fine (servo and ABS function).

 

Then (out of the clear blue), I'll apply the brakes, glance down at the dash I'll get the two lites flashing at a 1hz rate; this is under and after normal braking. Brakes are still operating fine, I pull over, turn off and restart the bike and clears the indication. Won't see it again for 500 miles or so. Other than it occurs within a few miles of initial (from cold) operation, nothing else indicative of a pattern (my research shows the sensitive low battery issue that affects some ABS systems is a startup phenomenon - the behavior I'm seeing does not resemble that scenario)

 

These are the original pads (w/36k on the bike). Brake fluid reservoirs (front and rear) are fine. Have NOT checked under the tank. In any event, looks like I'll be minimally doing an inspection followed by replacement and bleed.

 

Any other thoughts?

 

Mike O

 

 

Mike, if the brake warning lights are flashing together at 1 Hz it isn’t brake fluid level (at least not supposed to be)..

 

If the brake warning lights are flashing ALTERNATLY at 1 Hz then you either have low brake fluid in one or both controller reservoirs,, or a defective sensor, or (possibly) a defective controller..

 

Twisty

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Unless this is a new 'low voltage situation', every one that I've researched occurs at or about the moment you start the bike for the first time (when engine/started are cold and current draw is the greatest). Here's another quote from elsewhere on the board:

 

If with ignition on the lights flash together but go to alternate flashing when you start the engine, it means low voltage while cranking. Means low battery, tired starter motor, corroded connections... any of this. After riding a few minutes, if you stop, shut off and restart, it should be OK.
If I recall correctly, this is a test sequence at startup time that requires a minimum voltage be detected for the ABS to believe it will function properly. Failing that voltage test, it will produce the diagnostic code stated in the quote above. What I'm experiencing (and is similar in description to yours) is NOT occurring at startup but well after I'm underway. What I'm reading into your explanation would indicate a weak charging system or discharged battery would produce the same diagnostic indication well after you're on the road and riding. I've ridden with an almost dead battery and never had the brake lights illuminate.

 

Does anyone know if the ABS voltage requirement is tested beyond at bike start up time?

Mike O

The first quote is describing the R1100RT and concurrent systems (pre EVO) they had two identical lights that would flash in unison until you started the bike and rode it a few dozen feet. Then you would hear the ABS system go "clunk" and the lights would go out. During the initial start-up sequence it was sensitive to the voltage dropping below a certain threshold and it would fault by blinking alternately. Since this was usually caused by the extra draw of starting a cold engine that had been sitting for a bit, but after driving a few miles the alternator replaced some of the drain, the engine had warmed up and was better lubricated and a restart didn't bring the voltage below the alarm level and the fault reset. I don't think the EVO computer's faults can be read with a volt meter anymore (you've got to hook it up to the BMW diagnostic computer). I believe the EVO's ABS is not as sensitive to the pre-EVO low-voltage alarm level and the warning lights should not flash alternately unless you've got a fault (though it still could be low voltage as the servos draw a LOT of juice). If you keep the bike on a tender, but the battery's capacity is down with aux lights and heavy servo use it could trigger a low voltage alarm (if the EVO system still has one), but I'm still suspecting a low fluid level. It's fine when the bike starts, but when the bike is still cold after the first braking (low fluid sloshes to the front of the largely empty reservoir triggering the float to set a low level alarm) and then as the fluid warms up from the engine heat and the heat of braking expands the fluid (as well as the dissolved water since the last bleed) slightly and it doesn't happen again until the next time the bike is cold. You do live in hilly country as well--that first braking downhill from the house could be the perfect circumstance to set it off.

 

I'd pull the calipers and see how worn the pads are. Have you ever had the brakes bled? You're going to need new pads pretty soon anyway (if you keep this bike living in the mountains) if you're not already overdue. Buy a new set of pads and unless the stock pads look less than 50% worn, push out the pistons enough to install the new pads, reinstall the calipers and take the bike out for a ride. If you've had the brakes bled once and the pads are replaced with new ones, the overflow might dribble a bit of brake fluid behind the right foot peg for a day or two. Just park the bike on some newspaper to catch the drips. If you get the same alternating flashing light fault, check out replacing your battery (you're not still using the original lead-acid one are you)? Is it bone dry yet? The dealers notoriously neglected servicing those old batteries--I've found many of them all but dry. If it's also still the stock one go ahead and replace it (you're due) and see if that solves your problem. All of these are fairly easy fixes to try that don't require you pulling the tank--which saves you a LOT of headache (pulling the tank is harder than doing the entire brake bleed once you've done it a few times).

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