Bleeding brakes

rugbyjack2005 · Sep 6, 2013

I have a 2003 955i Speed Triple which I have had for a few years now and thought it was about time that I changed the brake fluid.

I took out the old fluid and put new fluid in and then begun to bleed the brakes however rather than bleeding them, I seem to have just put a load of air into the system as the front brakes don't work at all now... I wonder if someone could help me understand where I have gone wrong?

With the reservoir cap off, I connected a bleed kit (with a none return valve so I didn't put it in a container of brake fluid) to the bleed nipple, loosened the bleed nipple on one side and started pumping the brake lever. I was expecting fluid to be pumped out of the bleed kit pipe like what happens when I bleed the brakes in my car but it looked to me as if I was actually sucking air in. Would I be right in thinking that where I went wrong is using a bleed kit with a none return valve and I should have just connected a pipe to a container full of brake fluid?

Thanks in advance for any help.

Mattson · Sep 7, 2013

By a non-return valve you probably mean one of those little aluminum things that have a plastic ball and a spring inside, I`ve seen about ten different interpretations of the subject, even owned about five-ish of them but have yet to see one that actually works!

From my own experience the surest ways to make it work are either putting a tube to the bleed nipple and just put your finger to the end as a valve and slightly lift it every time you press the lever and close the end when you let the lever go, continue as long as needed (might take a while) and then put the end of the tube to a can of clean unused brake fluid and proceed the same as doing a car brake bleed.

HOWEVER, bleeding a completely empty motorbike twin front brake system can be a total bitch, no matter what you do the !"#¤%& just wont-start-to-pull-fluid!!! One old geezer that restores old vintage Ducatis once taught me a neat little trick:

-Take the reservoir cap off but do not put any fluid in there
-Go to your local pharmacy or wherever they sell them there, and buy a big ass syringe, big enough that the bleed tube can be fitted to the spout.
-Pull the syringe 2/3 full of fresh brake fluid, make sure there`s no air in the tube or the syringe.
-Attach the tube to your bleed nipple and open it half a turn
-SLOWLY press the syringe piston in and watch air bubble to the reservoir, repeat on both sides
-To be sure it`s a good idea to do a traditional bleed too just like in a car (open the valve, press brake, close valve, release brake etc)

And folks, do remember that brake fluid is highly corrosive and can damage painted surfaces!!! Remove any spills immediately with a highly vaporising solvent like xylene, thinner, gas, brake cleaner spray etc!!! The fluid will also destroy the syringe and the clear plastic tube you`re using, do NOT save them for later use cause even if they SEEM fine, the insides have dissolved into the fluid and using them again will cause dissolved plastic to enter your brake system!!!

rugbyjack2005 · Sep 7, 2013

Mattson said: ↑

By a non-return valve you probably mean one of those little aluminum things that have a plastic ball and a spring inside, I`ve seen about ten different interpretations of the subject, even owned about five-ish of them but have yet to see one that actually works!

From my own experience the surest ways to make it work are either putting a tube to the bleed nipple and just put your finger to the end as a valve and slightly lift it every time you press the lever and close the end when you let the lever go, continue as long as needed (might take a while) and then put the end of the tube to a can of clean unused brake fluid and proceed the same as doing a car brake bleed.

HOWEVER, bleeding a completely empty motorbike twin front brake system can be a total bitch, no matter what you do the !"#¤%& just wont-start-to-pull-fluid!!! One old geezer that restores old vintage Ducatis once taught me a neat little trick:

-Take the reservoir cap off but do not put any fluid in there
-Go to your local pharmacy or wherever they sell them there, and buy a big ass syringe, big enough that the bleed tube can be fitted to the spout.
-Pull the syringe 2/3 full of fresh brake fluid, make sure there`s no air in the tube or the syringe.
-Attach the tube to your bleed nipple and open it half a turn
-SLOWLY press the syringe piston in and watch air bubble to the reservoir, repeat on both sides
-To be sure it`s a good idea to do a traditional bleed too just like in a car (open the valve, press brake, close valve, release brake etc)

And folks, do remember that brake fluid is highly corrosive and can damage painted surfaces!!! Remove any spills immediately with a highly vaporising solvent like xylene, thinner, gas, brake cleaner spray etc!!! The fluid will also destroy the syringe and the clear plastic tube you`re using, do NOT save them for later use cause even if they SEEM fine, the insides have dissolved into the fluid and using them again will cause dissolved plastic to enter your brake system!!!
Click to expand...

Thanks for your help. I have done it now. The problem was that when I released the lever, it sucked more fluid/air in than pressing the lever pushed out so I was in effect just sucking air into the system. To resolve this, I simply opened the valve, squeezed the brake lever, closed the bleed valve and repeated until the system was clear.

Mattson · Sep 7, 2013

Well, that`s the way to do it anyway, sometimes it just doesn`t start working no matter how long you do it so that syringe thing is a good trick to know in case you need it, the guy told me that old Ducati rear brakes that have long horizontal lines need to be bled that way or they will blow bubbles endlessly.