New master cylinder

tshadow6

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I installed my new master cylinder for my project. I cannot get the brake fluid to flow down to the caliper. I know there is a lot of air in the hoses. How long should it take to vacuum out the air? I have a hand pump. How about gravity feed? How long should that take?
 
I installed my new master cylinder for my project. I cannot get the brake fluid to flow down to the caliper. I know there is a lot of air in the hoses. How long should it take to vacuum out the air? I have a hand pump. How about gravity feed? How long should that take?

When I do brake work, I find an easy method is to pre-fill the brake lines. I take the brake line(s) to the bench and fill the lines using a syringe. I then fill the caliper(s), and re-attach the full brake line(s). Fill the M/C and then a very small of bleeding at the caliper(s), and the job is done.
 
Front. I might get the one piece brake line from Mikexs to make keep it simple. Where do I get a syringe? I've heard of that method before.
 
Gravity is your friend and yes leave the cap off master cylinder and keep it filled.
You just might have a bubble in the master cylinder.
If your bleader is leaking air through the threads while vacuming, A little bit if teflon tape will take care of that then pump away. it wont work will the it leaks air.
I've walked away with the cap off and let the bubbles rise to the top and out of master cylinder. At the time I didn't know it was going to work out that way we were just tired of trying and came back after taking a break and we had brakes go figure.
My favorite way is to bleed it before installing the master on bars. that way you have the air out of it before you have the lines on. You can do it on the bars but it an get fluid on your paint :eek:
 
I find master cylinders to sometimes be a bear. You can spend a half an hour pumping and bleeding the darn things, they eventually come around. One trick is to pull the lever in, zip tie it and leave it overnight. Air seems to bleed up and out quite nicely that way, without the hassle. Air does not move all that quickly thru brake fluid, so just have patience.
 
You can get a plastic syringe from your local pharmacist. Mine just gives them to me. 1/4" vinyl tube fits it.

roy
 

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Partial success! I gravity fed fluid into the upper brake line. I think there is some kind of clog in the connection leading to the lower brake line. I am going to have a one piece line made at a local industrial hose shop.
 
I have found that when installing a new or rebuilt M/C you need to bleed just the M/C first.
With the M/C mounted, leave the brake line unhooked. Place your finger tip over the hole the banjo bolt threads into, slowly pump lever. As you pull the lever air gets pushed out around your finger tip. As you release the lever your finger tip seals the hole, this makes the fluid get drawn out of the resevour. After a few pumps you should get fluid spraying out past your finger tip.
Now hook the line up. It should bleed ok then.
I have an extra set of bars I use for this. I do this bleeding off the bike. I also bleed the line the same way Hook the line up, hold the line up above the M/C, seal the end with my finger and thumb, bleed, once I get fluid I hook the line to the next thing in the system, With a two line system I hook the line to the junction and the next line, hold up, bleed. Hook the line to the caliper, hold up bleed.
Once all bled I install the assembled system on the bike.
A one piece line is quicker.
Leo
 
I re installed the caliper for the front brake today. I think I have to reverse the brake line. Are the fittings on the brake line universal? In other words, does it matter which end of the brake line is hooked up to the MC or the caliper?
 
As far as function goes, no it makes no difference.
On some lines the angle of the banjo fitting may fit better one end or the other.
Leo
 
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