QuestionI am replacing the brake lines on my 2000 XR650L starting with the front brake. After draining the fluid, replacing the brake line, filling the reservoir, pumping the brake lever, sucking the fluid through the caliper with a vacum pump I still have no pressure at the brake lever.....when the reservoir is removed from the bike and the line disconnected no fluid flows from the (disconnected) connection to the line when brake lever is pumped. What am I doing wrong and how do I bench bleed or do I even need to?
Your reply would be a great help to this mystery, also got to do this again with the rear brake so if that is the same procedure please advise, thanks in advance.
AnswerHi Hugo...
Replacing a brake line can be frustrating for sure. Here's what ya do:
Start with the master cylinder mounted securely on the handle bar so that the reservoir is level. Fill it to the proper level. MAKE SURE THE FLUID LEVEL NEVER GOES DOWN BELOW HALF!!! Unbolt the brake line at the master, then hold your thumb against the hole on the master. When you pull the brake lever a few times you should start to feel the pressure pressing against your thumb. Once you feel that pressure, release the brake lever and remove your thumb. Connect the brake line to the master (making sure you have new washers on each side of the banjo fitting) and tighten it snuggly. Now disconnect the brake line from the brake caliper down at the front wheel. Place one finger on one side of the brake line banjo and your thumb on the other side, as if you are trying to keep fluid from leaking out. Now pump the brake lever about 5 times, hold it in, and then release the pressure on your fingers. Re-engage the finger pressure before you release the brake lever. What you are trying to do is to prime and bleed the line from the top down. You'll need to do this many times, as the master brake cylinder is not really a pump as much as it is a plunger. Eventually, when your fingers are plugging the banjo at the caliper and you keep pumping the brake handle, you should start to feel pressure against those fingers... when you do, hook the brake line onto the caliper (again, make sure you have new washers on each side of the banjo), and do a "bolt bleed" at that fitting. You should now see fluid either seeping or squirting at that banjo joint. Tighten all the lines and do a regular bleed at the bleed nut on the caliper. If after doing all this, your brake lever is still spongy feeling, you may have to continue the bleeding process at each place we went thru earlier. A brake master cylinder can only cause pressure if ALL air is removed from the lines. The best way to remove ALL air is by bleeding the system at every joint, not just at the bleeder nut on the caliper. And Hugo.. I gotta admit that some of those vacuum brake bleeding kits are a bunch of hype.. they say they make it easy, but sometimes the best solutions are found in old school methods. Most shops charge more to replace brake lines then to do a brake pad replacement because it can take a while to get brake pressure up to par. Most of us use some sort of bleeder kit, but even so, those kits take time to get used to. Look at it like this... when a brake system is working properly, the movement of the brake pistons is like a millimeter or so... which means the brake master hardly qualifies as a pump, but rather a pressure maker... now consider that the fluid has to be moved thru over two feet of hydraulic lines... you start to see that brake line bleeding can take time and patience. Hope this little novel I typed helps you out Hugo!!! Let us know if ya need more assistance!!!
Jack
PS: The rear is pretty much the same as the front!!
