Changing Brake Fluid on an 02-Later

Changing Brake Fluid On An ’02-later K1200LT Integral Brake System – Ver. 1.0

1. Background

a. Warnings

There’s no getting around this: This is maintenance work on BRAKES! If you attempt to do any of the following work, YOU MAY BE PUTTING YOURSELF, YOUR PASSENGER, BYSTANDERS, and YOUR VEHICLE in danger of INJURY or DEATH. While I have performed the procedures discussed below, I did so because I could control the work being done, and because I was willing to accept the potential consequences of my actions in maintaining my own vehicle. I CANNOT, AND WILL NOT, BE HELD RESPONSIBLE FOR ANY DAMAGE, INJURY OR DEATH ARISING FROM ANY USE OF THE INFORMATION THAT FOLLOWS.

Next, while I believe I understand the Integral system well enough to attempt the work myself, YOU have to understand I have not been trained on, or have access to any in-house BMW documentation on, the Integral system. Accordingly, I further cannot guarantee the accuracy of any of the following. So, if you in any way make use of the following information, YOU DO SO WITH KNOWLEDGE of the risk the information may not be accurate, and that injury, death or property damage may result.

Don’t even think about doing this work without having at hand, and having read beforehand, the “official” brake bleeding procedures in the Repair Manual! (Pages 00.51-00.62 in the Integral ABS Supplement). The procedure below is NOT a substitute for the Repair Manual, it is a complement to it. If you don’t understand the Repair Manual procedure, and why the steps below deviate from the BMW procedure, you shouldn’t be doing this work.

Read this ENTIRE document – there’s info in the earlier sections that I don’t bother repeating later. Then re-read it.

Finally, recognize that if the steps in the following procedures are not properly accomplished, or executed without understanding the cause and effects of each step, you may render the braking system unsafe for road use. In this situation, the only safe course of action will be to trailer/flatbed the bike to a dealer to have the brakes restored to operating condition – at your expense, not mine!

Oh, and don’t be ham-fisted with the various fittings in the system – there’s a number of aluminum and brass pieces, and even a small amount of excess torque may be enough to strip out the fittings.

1 b. Integral System Design

There are a few fundamental concepts that must be understood before you decide whether to do this work yourself. In many ways, by the time you’re done reading this document, you would be right in thinking “Oh, that’s all there is? That’s simple!” – but that will be only after you have learned the overall operation of the Integral fluid systems.

Basic principles, in no particular order:

1. Unlike conventional hydraulic brakes, there is no fluid connection between the front and rear master cylinders and their respective brake calipers.

2. There are two separate fluid circuits for each of the front and rear brakes (four total).

3. Each of the front and rear brakes has:

a. A “control circuit” – a fluid circuit from a master cylinder (front: handlebar mount; rear: behind right foot peg plate) to the Integral pump,

b. A “wheel circuit” – a fluid circuit from the Integral pump to the respective front or rear caliper(s).

4. The four circuits meet at the Integral pump.

For simplicity, you can think of the two control circuits (pipes 2, 4 below) entering into control chambers in the top half of the pump (at the two thick black arrows at the middle of the pump unit), and the pump-powered wheel circuits (pipes 1, 3) emerging from pump chambers in the lower half of the pump (at the two thick black arrows at the bottom of the pump unit). Front control and wheel circuits on the rider’s left side of the pump unit; rear control and wheel circuits on the right.

The hoses 7, 8 leading into the lower right side of the Integral pump unit are the hoses from the front and rear halves of the dual-chamber rear reservoir in front of the right saddlebag. These supply the front and rear wheel circuits with fluid to pump to the calipers.

2 5. When a brake lever is pulled or pushed, the signal from the lever’s brake light microswitch not only actuates the brake lights, it also sends a signal to activate the Integral unit pumps in the wheel circuits.

6. The pressure output from the pumps to the wheel circuit(s) is modulated (controlled) in proportion to the pressure in the control circuit created by the operator (using the brake lever or pedal).

3 7. Again, for simplicity of explanation: While there is no fluid connection between the control circuits and their respective wheel circuits, the pressure applied in a control circuit is applied to the wheel circuit by a piston separating each pair of control and wheel circuits.

8. When the Integral system is operational, the pressure sensed in the control circuit is used to control the pumps, so the piston between the control circuit and the wheel circuit appears to be largely irrelevant. The pistons are important, however, when the Integral system is disabled.

9. When no electrical power is present, the pumps do not create pressure in the wheel circuits. In this case, the pressure in the control circuit created by the operator with the brake lever is applied to the piston between the control and wheel circuit chambers in the Integral unit, thereby manually creating pressure in the wheel circuit to operate the calipers.

10. Within the Integral unit, cross-connections are provided to create the “integrated” or “linked” functions. The cross-connections consists of small passages from each control circuit to the other control circuit, with small pistons at the end of each cross-passage for applying pressure on the other control circuit. (FWIW: the small piston size is apparently why cross-connections are not very effective when in unpowered mode). A bleeder for the rear cross- connection passage can just be made out in the above pic, in the recess directly above pipe 3.

11. There are three brake fluid reservoirs in the system:

a. Front control circuit – hand lever master cylinder reservoir b. Front wheel circuit – rear half of rear 2-chamber reservoir c. Rear control circuit and rear wheel circuit – sharing front half of rear 2- chamber reservoir

12. Because the front control circuit has no fluid connection to the front calipers, the fluid level in the front master cylinder should never decrease (unless there is a leak somewhere in the control circuit).

13. Because the rear control circuit shares its reservoir with the rear wheel circuit, the fluid level in the reservoir will decrease as the rear pads wear.

14. The pumps operate at two speeds, low and high. It appears that the output of the pumps is modulated as needed (servo controlled valving??) to variably decrease the pressure from the pump to match the level required in the wheel circuit in response to the control circuit demand.

4 c. Fluid Changing vs. Brake Bleeding – the Difference

If there is air present in any of the four fluid circuits, then “bleeding” in accordance with the procedure in the Repair Manual is required to ensure all the air is eliminated (thereby ensuring the pumps can create pressure in the wheel circuits as fast as required).

For our purposes here, a “fluid change” is the displacement of old fluid by new fluid where you are starting with a system in which there is *no* air present, and none is introduced into system during the fluid change.

Avoiding introduction of ANY entrained air provides the opportunity to skip many of the steps in brake bleeding procedure in the Repair Manual, while flushing essentially all old fluid out. Making a mistake, and getting ANY air in the system will cause you much grief and money (unless you get extraordinarily lucky and can properly execute the Manual’s system fill and bleed procedures). Not to mention the joy of non-riding carriage of the bike to your dealer, who will have a wide, condescending grin on his face. You don’t want that, do you?

2. Brake Fluid Change Principles

a. The Repair Manual brake bleeding procedure generally requires several steps, summarized below:

1. Control circuits – uses brake levers to push fluid out a. Bleed at fill point next to Integral unit. b. Bleed upper control chamber in Integral unit* c. Bleed at integral passage in Integral unit* d. Bleed again at fill point next to Integral unit

* Requires special tool to reach bleeder screws on Integral pump.

2. Wheel circuits – uses Integral pump motors to push fluid out

a. Fill circuit with a syringe apparatus attached to a caliper bleed screw, from the caliper back through the Integral unit’s pump chamber to the master cylinder and reservoir.

b. Bleed the freshly filled wheel circuit using the Integral pump motor to push fluid out the caliper bleed screw.

3. Finally: Conduct a MoDiTeC “Bleed Test” – The dealer’s MoDiTeC:

a. Reads/clears stored codes. You are guaranteed to have stored “low reservoir level” codes, as the pumps will cause the levels to trip the reservoir level sensors during the procedure. Once the levels are restored, the error is no longer reflected on the dash warning lights, and the low level event just sits in the stored memory until later cleared.

b. Checks a variety of system components for proper operation.

5 c. Checks for sufficient “residual” pressure – this is essentially a check that there is no significant compressible air in the system, so the Integral pumps can immediately build and apply pressure to wheels. During the Bleed Test, the technician applies brake levers and holds pressure in a “green band” shown on the MoDiTeC display while MoDiTeC runs its tests. I observed a Bleed Test once, and I believe the MoDiTeC drives the system at varying pressure, so this is more than “squeeze and hold pressure for “x” time test – the concern is not just whether the system can generate and hold sufficient pressure, but also how quickly pressure rises.

3. My Approach to Brake Fluid Change

The following is all based on the recognition that there’s no air in the four control and wheel circuits at the start of the typical brake fluid change. This eliminates the need for some of the Repair Manual bleeding procedure steps.

a. Repair Manual bleeding procedure steps generally not required:

1. Control circuits (referring to the above Repair Manual bleed steps)

a. With no air in the system, there is no need to bleed at fill Integral unit fill plugs, since fluid will be purged downstream anyway

b. For the same reason, there’s no need to bleed at a fill point a second time, as there won’t be any new air to purge from the system.

c. The Integral cross-passages do not *need* to be bled, as a practical matter. Here’s the one place where fluid is not changed (at least directly). The bleeders for these passages are recessed into the sides of the Integral unit, and access requires a BMW special tool. If I had the BMW special tool, I probably would change the fluid in these passages, but rather than abandoning the entire procedure over this, I decided to bypass the passages. I justify not purging these passages on the basis that the cross-connection passages are very small volume and thus the amount of fluid is very small, at least some of the fluid is subject to exchange (and thus gradual dilution over time), and finally because the passages are located where water accumulation should not be a major issue. You need to decide for yourself whether this is an acceptable choice for you.

d. That leaves only the need to bleed old fluid from the control circuits from their respective master cylinders to the control circuit chambers. These chambers are bled through their long brass bleeders at the rear of the pump unit. The bleeders are near the top right of the pic below:

6 2. Wheel circuits

a. Because there is no air in the circuit, there is no need to back-fill the circuit with a syringe through a brake caliper bleeder.

b. Fluid change in the wheel circuits, at least conceptually, follows conventional feed/bleed techniques, except for the use of the Integral unit pump motors rather than a brake lever to push fluid out of the circuit. Before anyone asks, vacuum bleeding from the caliper is not allowed by the Manual, and I never tried it, so I have no way of knowing whether it would work (I’m doubtful).

7 4. Procedure

a. Tools Needed/Desirable

1. Clear tubing to attach to bleed nipples, with purge bottle at other end.

Note: A suggestion (credit to David Shealey): An excellent tool for this, if you can get one, is an IV bag and tubing, hung above the bleed point. This will allow easy, trapped escape of fluid from the bleed nipple, with no chance of air returning down the tubing.

2. A variety of box/open end wrenches – seems like every bleeder screw was different! Among those I recall: 7mm pump bleeders, 11mm rear caliper, 10mm front calipers, 13mm if removing the factory fill fitting (grub screw adapter).

3. DOT 4 brake fluid – I prefer to use colored fluid to help make it more apparent when “clean” fluid appears in the clear hose. I typically use ATE Super Blue Racing brake fluid, available at most shops catering to sports car/SCCA racers.

4. BMW bleed screw and dust boot (P/N 34 21 2 330 310) – needed either to be inserted into factory fill fitting at right front caliper to permit bleeding, or to replace the factory fitting entirely

5. Fluid disposal container (a fair amount of fluid is used/collected)

6. Rags/paper towels – lots

7. Two syringes or mini-turkey basters for removing old fluid from reservoirs and refilling the reservoirs without spilling/splashing.

8. A small, strong flashlight to backlight the rear reservoirs.

b. Bike Prep

1. Remove tupperware: L&R upper side panels, L&R battery covers (requires passenger footpeg plates be removed)

2. Remove dust covers on long pump bleeders and calipers

3. Turn on the ignition, and wait for the Integral unit for complete its start-up self- checks. Then apply the brakes while you listen for the sound of the Integral pumps – notice/learn how fast they get up to speed/build pressure. You’ll need to remember this sound for comparison checks when you do your final tests.

4. Optional: Disconnect headlight or turn off Euroswitch to save battery.

8 c. Front Control Circuit Fluid Change

1. Turn the bars full left (put the brake reservoir at its highest, most level position). I also advise applying a strap to the front wheel to hold it to the left.

2. Remove front master cylinder cover and gasket – have a paper towel present to catch the inevitable drips. Even if you have removed the fairing panels, you should consider covering bike parts under this with plastic (e.g., a garbage bag).

3. Siphon off the old brake fluid ONLY down to just ABOVE the hole in the ridge at bottom of reservoir – DO NOT let air into this hole.

4. Refill reservoir with new DOT 4 brake fluid.

5. Install the clear hose on the end of the long bleeder at the driver’s left side at the rear of the Integral pump. I stuffed a rag under the bleeder where it meets the pump unit wall, just in case a trickle of fluid ran past the bleeder threads.

6. IMPORTANT! Lay a rag or paper towel over top of front brake reservoir! When the brake lever is released after being squeezed, a “spurt” of brake fluid *shoots* upward out of the hole at the base of the reservoir – and it is aimed *directly* at the right windshield wing and the side of the nose fairing/mirror body.

7. Apply and hold the front brake lever, then open the long bleeder at the Integral pump. When the brake lever reaches the throttle grip, close the bleeder, then gently release front brake lever. To reach the bleeder while squeezing the brake lever, I stood on the right side of bike and reached over the frame to reach the 7mm wrench sitting on the bleeder and sticking out of the left side of the bike.

8. Repeat step 7 until new fluid emerges from bleeder – check reservoir level and refill frequently to avoid at all costs letting the level get low enough to let air into the control circuit – a major headache for you if air enters.

Note: Don’t be tempted stop when the first signs of new fluid emerge – pass enough through until you get *completely* clean fluid. Remember, you’re diluting a volume of old fluid in the upper chamber, so you need to pass enough new fluid through to get, say, at least 90% of the old fluid purged out.

9. When clean fluid is coming through, close and tighten the bleeder and recap with its dust boot. Take care to not over-torque the bleeder – brass threads going into aluminum threads won’t take much torque. Imagine what you’ll have to go through to save the pump body (thread tap? helicoil? pump unit removal/bleeding?) – that should ensure you won’t go too far with the wrench!

10. Apply/hold the brake lever to verify it is not spongy and remains firm. 11. Top off the handlebar reservoir to the required level in the sight glass (illustrated in the Owner’s and Repair Manuals). Reinstall the master cylinder gasket and cover.

9 Note: Be sure you wipe off excess fluid in the gasket seal edges to minimize/prevent dribbles down the sides of reservoir when the cover screws are tightened down. Even then, some fluid may still be trapped in the gasket or cover ridges. If so, it will show up on the outside of the reservoir, and maybe even on your paint the next morning – so cover the area under the master cylinder until you are positive no fluid is going to drip.

d. Rear Control Circuit Fluid Change

1. Remove the screw-on cap on the front half of rear reservoir

2. Siphon out the old brake fluid – ONLY down to just above the top of the hose connection at the rear, bottom of the front half of the reservoir (note: this is not the hose at the front bottom of the front half of the reservoir)

3. Refill the front half of the rear reservoir with new brake fluid.

4. Install the clear bleeding hose at the long bleeder on right (inner) side of the Integral pump unit. Stuff a rag under the bleeder/pump junction.

Note: Getting the clear hose on the inner long bleeder is a real pita – there is very little clearance between the end of the bleeder and the adjacent computer box. Patience, and perhaps a pair of needle-nose pliers to help walk the hose over the nipple, is required.

10 5. Apply and hold pressure on the brake foot lever, then open the bleeder at Integral pump. When the brake lever reaches the end of its travel, close the long bleeder, then gently release foot lever.

6. Repeat step 5 until new fluid emerges from the long bleeder – check reservoir level and refill frequently.

7. When clean fluid is coming through the long bleeder, close and tighten the bleeder and recap with its dust boot. Don’t over-torque the bleeder.

8. Apply and hold the foot brake lever to verify it is not spongy and remains firm.

9. Top off the front half of the reservoir to the required level. Leave the cap off if fluid is to be changed in rear wheel circuit.

e. Rear Wheel Circuit Fluid Change

1. Ensure the fluid level is near the top of front half of rear reservoir.

2. Attach the clear hose to the outer rear caliper bleeder.

CAUTION: Changing fluid in the wheel circuits requires use of the Integral unit pumps. THE INTEGRAL PUMPS CAN DRAIN THE RESERVOIRS SHOCKINGLY FAST – you must not hold the caliper bleeders open for a long period, lest you drain the reservoir and draw air into the Integral unit.

3. Turn the ignition on, and wait for the Integral unit to complete its start-up self-test routine.

4. Lightly depress the foot brake lever until you hear the Integral pumps just begin to run – maintain light pressure to keep the pump in its low speed range.

5. Keep the pump running while cracking open the rear caliper bleeder.

6. Close the bleeder after a short period to prevent the reservoir from draining, then release foot brake lever.

7. Repeat steps 4-6 until new fluid emerges from the caliper bleeder.

8. Once sufficient new brake fluid comes from the caliper, close the outer bleeder, reinstall its dust cap, and then install the clear hose onto the inner bleeder.

9. Repeat steps 4-6 until new fluid emerges from the inner bleeder, then close the bleeder and reinstall its dust cap.

11 NOTE: At any time between the multiple lever actuation/bleeder opening cycles, you can turn off the ignition – you just need to let the self-test complete when you turn the ignition back on before starting the next bleed cycle.

10. Top off the front half of the rear reservoir to the max level line, and then install the screw cap.

11. Test the brakes by applying the foot lever while the ignition is on (after the self- test is complete). If no air has been introduced into the system, the pump should immediately build pressure in the wheel circuit – the pumps should not d-rrr-aaa-ggg slowly up to speed. (BTW, this is why you should have listened to the pump operation during the bike prep steps to know what “right” sounds like!) If it sounds like the pumps are taking longer than normal to get up to speed, you may have air in the system, and need get the bike to a dealer – SAFELY!

f. Front Control Circuit Fluid Change

1. Remove the screw-on cap on rear half of rear reservoir

2. Siphon out the old brake fluid – ONLY down to just above the top of the hose connection at the rear, bottom of the rear half of the reservoir

3. Refill the rear half of the reservoir with new brake fluid.

4. Attach the clear hose to right front caliper bleeder.

CAUTION: THE INTEGRAL PUMPS CAN DRAIN THE RESERVOIRS SHOCKINGLY FAST – you must not hold the caliper bleeders open for a long period, lest you drain the reservoir and draw air into the Integral unit

5. Turn the ignition on and wait for the Integral unit to complete its start-up self-test routine.

6. Lightly squeeze the front brake lever until you hear the Integral pump just begin to run – maintain light pressure to keep the pump in its low speed range.

7. Keep the pump running while cracking open the caliper bleeder.

8. Close the bleeder after a short period to prevent the reservoir from draining, then release the hand brake lever.

9. Repeat steps 6-8 until new fluid emerges from the right caliper bleeder.

10. Close the bleeder and reinstall its dust cap. Install the clear hose onto the left front caliper bleeder

11. Repeat steps 6-8 until new fluid emerges from the left front bleeder.

12 12. Close the left front caliper bleeder and reinstall its dust cap.

13. Top off the rear half of the rear reservoir to max level, then install its screw cap.

14. Test the brakes by applying the hand lever while the ignition is on. If no air has been introduced into the system, the pump should immediately build pressure in the wheel circuit – the pumps should not d-r-a-g up to speed. If it sounds like the pumps are taking longer than normal to get up to speed, you may have air in the system, and need get the bike to the dealer – SAFELY!

15. Clean up your mess and put all the Tupperware back on! Reconnect headlight. Verify no leaks at reservoirs, Integral unit, master cylinders, calipers.

16. Operate brakes with the ignition off to verify they stop the bike under human- pushing power.

17. Turn ignition on and wait for self-test. Confirm no error codes (alternate warning light flashes, as opposed to the normal single light flashing until the bike starts rolling). If no codes, gingerly(!) start to test drive (with engine running) at *very* slow speed in a location where you can be sure you can stop without hitting anything if the brakes are responding poorly. If ok, gradually increase speed/test brakes in 5 mph increments until you are confident they are operating properly.

18. Optional: Drive to dealer and ask for (and be willing to pay for!) a quick confirmation check on the MoDiTeC to clear old codes and have the Bleed Test performed to assure yourself all is well.

13 Final Notes:

1. If I were pursuing perfection, I would follow the Manual’s requirement for using the special tool(s) to push the caliper pistons back into their bores (watching to ensure the rear reservoirs don’t overflow). This would ensure that every possible drop of old brake fluid was out of the calipers before the wheel circuits were bled. That is a better, but IMO, not necessary, way to go.

In the above procedures, it is assumed that your brake pads are in relatively fresh condition (like they were on my bike), and thus there wasn’t much fluid to be displaced from behind the caliper pistons by forcing them back the rest of the way into their bores. That may not be the situation if you don’t have relatively fresh pads. If your pads are thin, I can’t think of a better time to install a new set(s).

An alternative which I will probably do the next time I do this job: After completing the entire wheel circuit procedure, push the caliper pistons back and allow the Integral unit to refill the calipers when the ignition is next turned on. This will push at least some of any residual old fluid in the calipers back to the reservoir, further diluting what was in the calipers. NOTE: I haven’t tried this yet, and I expect it will generate a code. I believe this code will clear itself after system restart, but, as I say, I haven’t tried it yet to confirm the theory, so no guarantees!

If you have the correct tool(s) to hold the caliper pistons back in their bores during the procedures, by all means push the pistons back before doing the wheel circuits.