Do I have to bleed the front master cylinder

[johnny1980]

I did the front brakes. Bleed the system like crazy but still wont build up enough pressure. Do I have to bleed the master cylinder and if so how do i do it? I have a 08 busa Any help would be appreciated

[mike1180]

You bleed through the nipples on the calipers and add fluid to the Master cylinder.
How are you doing this?
There is a DIY thread in maintenance that tells how to do it right.
If you can't build pressure, you still have air in the system.

[craigntx]

done brakes many times w/o bleeding

[EarlyBird]

Ok... I have done front brake lines on my 08 busa and used the method I use when I service the brake system each year. I do bleed the brake system on my bikes yearly. I usually suck out the fluid out of the master cylinder first. Then add new fluid. Then I open one bleeder on the brake caliper and use a mighty vac... or a special tool I have to suck the fluid down from the master cylinder. Once I see the level drop in the master cylinder to half... I close the bleeder off. Then I go to the other side caliper and do the same thing. Once I have gotten done that. I top off the level again in the master cylinder. Make sure the bleeder on the calipers are closed. I pump the brake master cylinder and then hold pressure on it. Pump the handle 3 to 4 times then hold pressure. I open the bleeder on one caliper. I repeat that a few times each side. Like 3 to 4 times on each side to insure no air is in the system. I know at first the lever has little feel, but after the 3rd or 4th time the lever builds back up. I hope this helps!

[johnny1980]

I did it like a video i seen. Both calipers when I bleed them the calipers stream fluid right out no bubbles or anything. Went from the passenger to the drivers side bleeding them watching the fluid in the master. Does the master cylinder go bad often?

[EarlyBird]

I did it like a video i seen. Both calipers when I bleed them the calipers stream fluid right out no bubbles or anything. Went from the passenger to the drivers side bleeding them watching the fluid in the master. Does the master cylinder go bad often?

No... I havent seen them go bad. Is it a soft lever after bleeding?

[2busa]

I open a nipple and never stop pumping. That says the master fluid is being pulled down, I better hurry up and pour more dot, as I watch it self empty at the master I do nothing else but pour.
Then I press the lever and close the nipple at the same time. All I see is fluid running out. There are no bubbles. I have that nipple up against the threads not blowing bathtub bubbles down the clear tube.

I then go up to the M/C banjo bolt, break that loose with a paper towel wrapped around the wrench and bolt. The lever is squeezed and then I tighten as I close the banjo bolt. The lever comes up real strong, no longer has that softer spongy effect. It is right there at the top, ready to put you on your nose you go for a handful.

[AJAY]

I rebuilt the master cylinder on my Miata last year (cause I'm cheap and I like doing stuff like that). But for once, I just could not get the brakes to bleed worth anything - just would not build up pressure. Never had that happen before. So I dug out the mighty vac pump and pulled fluid through to the calipers. After that, the master cylinder worked just fine. I guess it had air trapped in it that just wouldn't budge.

Harbor Frieght sells a little pump that looks just like the Mighty Vac, but a lot cheaper. Probably made in the same factory in China.

[johnny1980]

I bought a mity vac thinking it was air in the lines. tI comes through with no air bubbles. But still has a very soft lever. i bleed both calipers over and over. Done them on cars and other bikes but this one has me puzzled

[EarlyBird]

After you bleed with the night vac. I usually manual bleed after it to ensure no air has gotten in the lines. I have had the mighty vac burn me a few times if I didnt manual bleed after that.

[johnny1980]

I used the mity vac to get the air out then manually did it a couple times still no success. I'm going to try it again tomorrow. Hope I can get it squared away. Never had an issue before thats why I was wondering if it might be the master cylinder or the lines

[EarlyBird]

Did you put new lines on? What brand if so?

[johnny1980]

No i'm using the stock lines I just need to double check to make sure no air is getting out somewhere

[GMbusa]

Yes. It's simple. Pump up the pressure and crack loose the banjo bolt at the master slightly enough to let some fluid out. It'll release the air that's trapped there and you'll have you brake feel back.

[AJAY]

I also have trouble getting a good bleed with the mighty vac, so it's a last resort and never gets used unless I'm trying to flush the lines with new fluid on a car.

Here's a trick to try: Figure out the position of the bike that will put the master cylinder mostly level. Take off the reservoir cap and make sure the reservoir is full. LIGHTLY tap the brake lever so it just barely moves. If you do it right, tiny air bubbles will pop up through the little hole for makeup fluid to enter the cylinder as the piston uncovers the port. I like starting this way because it lets trapped air out of the top of the line instead of having to pump it all the way down through the lines to the caliper. You won't get out all the trapped air, but you can definitely get out some this way.

[jphilipson]

Yes. It's simple. Pump up the pressure and crack loose the banjo bolt at the master slightly enough to let some fluid out. It'll release the air that's trapped there and you'll have you brake feel back.

+1, there are some vids on the mighty vac site, they show the whole process. But yes, you should bleed it if you want all of your brake feel back.

[BATTMAN]

Did you do the left side first? You have to do the furthest line first and then do the closest line.

[johnny1980]

Do you start with the left caliper first? All of the videos show working the the right side first could be where I am going wrong big time

[nabusa]

I was having the same issues. What I realized is that I was not closing the nipples on the calipers all the way and some air would get back in. Not saying that your not, but make sure those nipples are closed all the way or air will get back in the line.