FYI: Front Brake Bleeding

A while back, I replacing the front master reservoir on my wife's K75S. While the system was open, I also put speed bleeders on the front calipers.

Because the system had been opened in three places, I expected it to take a while to bleed. But not a half an hour! I kept going back and forth between the front calipers. I wasn't getting much air, but I was getting NO "pedal". I tried the conventional "up down" method on the brake lever and I also tried my vacuum bleeder. Still not much air but NO "pedal".

It seemed like the master was not bleeding properly, like when you don't "prebleed " a master on a car. But I am not aware of a procedure to "prebleed" the bike master.
Besides, I hadn't had this problem when I rebuilt the master cylinder last September. Everything bled fine with no problem.

Up to this point, I had had the bike on the centerstand with the front wheel pointed straight ahead to facilitate going back and forth between the two front calipers.

For some reason, I turned the front wheel all the way one way (sorry, I don't remember which way, but you only have two choices). I got a "pedal" in two pulls!!!

Obviously the angle of the master, when the wheel is pointing straight, was trapping an air bubble in the master.

So, If you ever have a problem when bleeding the front brakes, try turning the front wheel all the way to one side (or the other).

EDIT: Turn bars all the way to the LEFT to get the air out of the master.

When you are done bleeding, leave the steering at full lock to the left overnight. You'll notice a difference in the morning.

I've also noticed that almost all new BMWs with remote fluid reservoirs have upper bleed nipples included.

jdiaz said:

When you are done bleeding, leave the steering at full lock to the left overnight. You'll notice a difference in the morning.

I've also noticed that almost all new BMWs with remote fluid reservoirs have upper bleed nipples included.

Click to expand...

Thanks for the tip.

I had thought that the successful bleed was at full left lock. Your comment confirms this.

I'm glad I have older BMWs. I'm not too keen on the idea of "bloody nipples"!!!!!

bleed'n

i use a low pressure - air compressor "suck type"- bleeder - even thru abs sys (sometimes u'l have to "tickle" "turn on" abs newer sys) to get sm bubbles out of abs unit..
always turn master cyl to highest point away from banjo fitting. air gets trapped in banjo fitting (tap banjo w/ plastic handle screwdriver) & or loosen banjo - 1/4 pull on brk handle to help expel air) & TIGHTEN ON NEXT PULL
ALWAYS PULL BRK CALIPERS all the way IN - like installing new pads " clean then lube" cyl pots before u push them in around seals / dust caps.
flush entire sys ft & rear - till clear.
ok after hrs of do'n stuff - move handle bar to far LT (master hi point) -
INSTALL A QUARTER inside of master cyl to "cover" return port hole (so it dont squirt UP every where)
THEN --- HINT
tap handle about 1/4 way in - several times - THEN LET SIT & WATCH FOR VERY SM BUBBLES TO COME BACK THRU RETURN PORT HOLE "AROUND QUARTER" do this a few times - wait at least 10 seconds in between tap/ pumps
till NO air bubbles. & handle is SOLID. if handle is not solid - u got bad lines / worn pads or air trapped in sys. REMOVE QUARTER
honestally OEM lines should be changed after 10 yrs (at least) - they degrade inside & crack - then clog - so u can have solid feel but low/ LTD brake pressure to pads.
no need for speed bleeders - HFright sells vacuum for $20 - flush sys every year.
THAT BRN COLOR IS SOME MOISTURE & DEGRADING LINES - KEEP IT CLEAR