Brake Flush

[budzee]

I would like to flush the brake fluid on my 99 LTC. Does this need special tools? Is this very difficult? Are there directions some where on this site? Thanks for any help.

[cfell]

Howdy, Budzee..
There is a "process" in the HOW section.. klik here:
http://www.bmwlt.net/ubbthreads/showthreaded.php?Cat=&Board=K1200LT&Number=162457&page=0&view=collapsed&sb=5&o=0&vc=1

Remember, you assume ALL responsibility using the documentation/process.

[was]

It is well worth reading the link that Channing provided, and follow all of the general procedure comments. However, on a '99 you do not have the Integral brake system that is described and pictured by Mark Neblett in his write up. It would be just fine to heave a big sigh of relief at this point. (By the way, the Clymer manual also states in one place that pre-'02 bikes have Integral brakes. I cannot comment from personal experience on 2000-2001 bikes, but my '99 does not.) On the '99 you have two separate fluid circuits one for the front brakes and a different one for the rear. The only place that the circuits interact is via the ABS system, and even there the brake fluid in one circuit does not cross over into the other circuit. So, for all intents and purposes, you flush the front brake circuit and the rear brake circuit separately, and you bleed any entrained air from each circuit separately. Some people flush they systems by opening a bleed screw and pumping all of the old fluid out of the circuit, then adding fluid and bleeding the air that has entered the circuit. Some people flush and add fluid at the same time, using the new fluid to push out the old fluid and (theoretically) stopping air from entering the system. I don't know anything about the pros and cons of the two methods. A couple of tips: on my '99 there were bleed screws already installed on both sides of the rear caliper (yes, the one caliper has two bleed screws, and yes, both sides have to be bled). However, on the front calipers (each of which has only one bleed point) the left caliper had a bleed screw installed and the right caliper did not. Instead, the right caliper had a fitting with a "grub screw" installed. Once you remove the grub screw you can screw a bleeder into the fitting. The bleeders are size 10 x 1 (double check that, I'm relying on memory here). The ones that I got at an auto parts store were too long, and I never got a good seal in the threads. BMW, of course, sells it's own. It is worth getting in my opinion. It looks like it might be possible to leave the BMW bleeder in the fitting and cover it with its rubber cap, but I just unscrewed it and replaced the grub screw. These parts can be stripped very easily, so use a very light hand in screwing them down. Bleeding the system requires bleeding at each bleed point on the calipers, and also bleeding at the ABS sensor, which is under the front seat on the left side of the bike. You will see 4 hard lines attached to the ABS sensor. At the top of the sensor, under little rubber caps, are 2 bleed screws. The front one is for the front circuit and the rear one for the rear circuit. The manual suggests bleeding in a specific sequence (calipers, then sensor, IIRC). The only other tip I have is don't use a vacuum brake bleeder. It won't do anything to harm the system, but I and several other people have had the experience that it pulls more air than brake fluid, either because it does not seal well around the bleeder or because the bleeder is not sealed against air intake. (Until I figured this out I thought that BMW must have plumbed an additional 1/3 mile of brake hose somewhere, all of which contained air.) Also, note that if you use the front brake lever to pump fluid through the system you need to cover the reservoir with something because brake fluid spurts up from the intake hole at the bottom of the reservoir with every pump.
Otherwise, have at it. No special tools (other than maybe the BMW bleeder), no special procedures. Good luck.

[wcarter]

Pastor Jack helped me bleed the brakes on my '99 in January. He had some "speed bleeder" type screw-in replacements. They were a no-name version that he found at a local auto parts store. Worked fine once we got them installed.

I think I could do it myself now that I helped an experienced user do it first time around. We used a syringe to suck out most of the old fluid from the top of the reservoir (keeping the level above the little hole to keep air out). Then we added fresh fluid in the top while pumping old fluid out the bleeder using a plastic tube so we could monitor the color. We kept going until clear-ish fluid came out, then tightened up the bleeders and topped off the reservoir. We did not use a vacuum device.

Jack noticed my rear pads were about shot. I bought some new ones later; I had to bleed some more fluid out of my rear brakes to retract the pistons so the new pads would fit. As best as I can tell, the speed bleeder-type valve kept air from sucking back into the lines.

I'll ditto what someone said about brake fluid tending to squirt out of the open master cylinder if you're not careful. We covered the painted areas with old towels just to be safe.

[sheldan2]

if you put a razor blade in the reservoir while pumping it will eliminate the splashing/ pumping out all over the paint work...