bleeding the master cylinder?

[lonesoldier84]

Just changed front brake lines and brake lever and handlebars.

Have been bleeding the lines for what seems like forever and there is very minimal movement but I do still get an occassional good squirt of brake fluid from the bleed screws and a light trickle most of the rest of the time and also some air coming out sometimes making a squishy sound. I am bleeding both calipers at the same time but sometimes switch to one at a time.

But this is getting ridiculous. There has to be something wrong this is taking way too long. I've bled my rear before and it never took anywhere close to this long.

Could there be air trapped in the master cylinder or banjo bolts that's just sort of sloshing back and forth? Is there a better way of bleeding at the master cylinder? If I undo the banjo bolts won't the crush washers be less than ideal to reuse?

I'm doing the manual pump method btw. Would getting a Mityvac pump do much better and pull the fluid through?

 

[Motogiro]

Are you making sure you are not running out of fluid in the reservoir and picking up more air?
Bleed the farthest caliper first (left side) then after no more air, bleed the right side caliper. Make sure you keep the master res. from grabbing any air. :rockon:

 

[lonesoldier84]

What do you take me for?!?

I am Lone from SuperTech Auto god damn it.


Lol, there has been no NEW air entering the system. I've been sure to keep it topped up. The fact it's moving SOOOO slowly through the lines has made that easy.

I'll give it another go tomorrow but will loosen the banjos as part of the bleed process then work my way down the system.

 

[Motogiro]

What do you take me for?!?

I am Lone from SuperTech Auto god damn it.


Lol, there has been no NEW air entering the system. I've been sure to keep it topped up. The fact it's moving SOOOO slowly through the lines has made that easy.

I'll give it another go tomorrow but will loosen the banjos as part of the bleed process then work my way down the system.

You shouldn't have to loosen anything.The bleed should be good to go right from the bleeder valves....
I'm outta here! See y"all in the AM!

 

[FinalImpact]

Are you sure the new lever is allowing the MC piston to come out all the ways? If its not, that'll block the port and make for real slooooooooooow progress even if you pump and release.

Personally I vote for doing the closest caliper first.

As we all know, air when suspended in fluid sticks to surfaces. With that thought, I tap on the caliper with something soft enough that it won't mar it, but solid enough to shock it ever so slightly which will dislodge trapped air. Do this more aggressively while you have pressure in the system and much lighter when the bleeder is open. You have three hands right? lol

Also, do not tap it in a direction that will collapse or depress the pistons. Tap it from the outer edge of the wheel. Does that make sense?

FWIW: I oppose vacuum bleeding. If for some reason you pull 25" of vacuum or more, you can effectively boil the liquid inducing more air into the system. This is not likely to happen unless the path to the reservoir is blocked (like yours?).

 

[RJ2112]

Just changed front brake lines and brake lever and handlebars.

Have been bleeding the lines for what seems like forever and there is very minimal movement but I do still get an occassional good squirt of brake fluid from the bleed screws and a light trickle most of the rest of the time and also some air coming out sometimes making a squishy sound. I am bleeding both calipers at the same time but sometimes switch to one at a time.

But this is getting ridiculous. There has to be something wrong this is taking way too long. I've bled my rear before and it never took anywhere close to this long.

Could there be air trapped in the master cylinder or banjo bolts that's just sort of sloshing back and forth? Is there a better way of bleeding at the master cylinder? If I undo the banjo bolts won't the crush washers be less than ideal to reuse?

I'm doing the manual pump method btw. Would getting a Mityvac pump do much better and pull the fluid through?

Lone,

The questions you are asking make me think it might be time to go back through the whole process to ensure you are doing the manual bleed effectively. Compared to the rear brake, the front lines are vertical..... much, much more difficult to push the bubbles out the bottom of the drinking straw. They keep travelling 'up' the line.

First sanity check is to use a strap to hold the lever in over night. If there are bubbles at the top of the line, they should migrate back into the reservoir.

If you are using the OEM lines, the little one that loops over the wheel between the calipers is a sure place to trap bubbles. It's an upside down U trap. A bubble in there, weakens both calipers.

 

[segue00]

Just get a Mityvac.

 

[TownsendsFJR1300]

Not noted above, make sure the master cylinder is at the highest point when bleeding the system. One caliber at a time.

You'll usually (as noted above) that air does collect in the upper piston in the master cylinder. Gently push the lever in and out, you should see small air bubbles come out. I've used that procedure with initially a mity vac and finish off the old fashioned way.

Note: if you use the Mity vac, open the lower bleeder valves slowly (as if you have a high vacuum and open it fully, you'll suck it dry again)...

BTW, are the brakes lines stock or after market? The aftermarket lines without the curve over the front fender are considerably easier to bleed...

 

[FinalImpact]

First sanity check is to use a strap to hold the lever in over night. If there are bubbles at the top of the line, they should migrate back into the reservoir.

RJ,
Maybe i misunderstood something here - but I don't agree. With the lever in, the path to the reservoir is closed! If anything, the air will travel up the line and sit there at the port.

The only time the path is open is when the MC piston is completely out. Which is what makes me the think the NEW lever has it partially depressed which closes the port so while manual bleeding, pulling the lever down, it only has a half cylinder full to press fluids to the calipers.

Lever In is a NO GO!

 

[joe1971]

Just get a Mityvac.

No those are an over priced pos.

This is the exact same set that Car Quest sells for nearly half the price of the MityVac, and it won't break on you.
Brake Bleeder And Vacuum Pump Kit & Other Vacuum Brake Bleeders - HFT

 

[Marthy]

The way I do it is bleed open at first. Open the bleeder, hook up your bleeding bottle and keep pumping + adding fluid (always new fluid, don't recycle!) Do both side until you don't see much bublle. Then comes the important part. Pressure bleed! With everything hook up, nipple close... put a bit of pressure on the lever and open the nipple, squise the lever down and hold it there then close the nipple. Keep doing that until the line is clear, goon the other side. Sometime you might need togo from sideto side few time.

One more thing. Pump slow and steady. The piston in the master is quite bigger then the hole in the line. Fluid traveling too fast will create turbulance (well, bubble)

 

[lonesoldier84]

Ok, from everyone’s posts:

1) Check the MC piston? It seems to be working fine as it is pushing the right place the right amount when looking at it from the outside. Are you suggesting I open the thing up somehow?
2) Lovingly and gently smash the caliper with a sledgehammer to nudge air pockets off the surfaces.
3) I am using SS goodridge lines.
4) I will get a vacuum bleeder if I have to tonight. Manual is a PITA. I will try to borrow one from a friend. If not I’ll try to find something locally.
5) No more bubbles seem to be coming out at the MC anymore that I can see
6) When the lever is out, there is no contact at all with the MC assembly. The piston should be fine.
7) I have been pumping quite fast. I will slow it down. I will take my time and enjoy it.


I'll get to it again tonight. I'll give it a go one time with a vacuum bleeder afterwards. I don't have time to keep messing around with it so will take it to a dealership Saturday morning if I have to and get them to bleed the system.

Track day is Sunday.

Everything else is sorted so overall I'm pretty pleased with my effort.

Next up after the couple days of trackdays will be trying to get my electrical system sorted for lighting etc. Going naked so have to install all the everything and the horn etc. And my brake lights aren't working either but I don't care about that for now. Right now I just want to get everything in order for the trackday.

Thanks for all the input though people.

 

[FinalImpact]

2) Lovingly and gently smash the caliper with a sledgehammer to nudge air pockets off the surfaces.

Did I say it like that? lol brakes are over-rated anyways! haha

As for the lever, pull the boot back and get a visual that the piston is out against the snap ring and the lever where it contacts the piston should have a tiny gap allowing some free play.

I mean this should be easy. fill the res, pull the lever firmly, attach rubber hose and wrench to bleeder, crack bleeder until lever touched grip (gentle but continuous pull), seal the bleeder, and slowly release the lever.

Once it begins to build a firm non-spongy feeling on the lever, apply pressure and tap on the calipers. Hold pressure, crack bleeder following steps above. Just make sure the MC never goes dry.

Lastly, the new pads need to be seated in before you hit the track (ride it). This should also firm up the lever as they match the rotor.

 

[lonesoldier84]

No new pads. I talked to a friend with a vacuum bleeder. Gonna go that route for now.

Hopefully it stops being such a PITA.

 

[FinalImpact]

opcorn: opcorn: opcorn:

 

[Boneman]

I put this together and followed it when I bleed mine when I installed my HEL brake lines. I started off using a Mityvac, but ended up finishing the bleeding the old fashion manual way!

http://www.bonemanfz6.com/Manuals/Brake Bleeding.pdf

Another tip I found out was to pull in the brake lever and cable tie'd it back to the handlebars and left it overnight. They were rock hard by the morning!