Banjo Bolt Bleed?

[MBH328]

Is it possible/desirable to bleed the banjo bolt on a master cylinder that already has a bleed screw?

After struggling with brake bleeding for a week, I still can't get a firm lever. I've bled the master cylinder and both calipers to the point where no bubbles are visible in the plastic tubing for 10-12 squeezes of the lever. It's a basically-new system with a brand new MC (transplant from an '07 CBR), new SS lines (Galfer Superbike), and completely rebuilt calipers with fresh software and new speed bleeders. I've tried the zip-tie trick (tie lever down overnight then re-bleed) with limited success, but the lever is still a little soft.

I have seen other threads on here talk about bleeding the banjo bolt, but not provide details...before I run off half-cocked and try something without making sure it's a good idea (like a take a power sander to my rotors:doh::doh, I'd like to verify what I THINK I should do:

1) Pump brake lever ~10 times and hold
2) Loosen banjo bolt 1/4 turn
3) Let brake fluid ooze/shoot out of the bolt into a catch-tray while holding lever
4) Tighten banjo bolt to Galfer torque spec and release lever
5) Re-Bleed entire system

If that's a just a terrible idea, my other thought is to perform a "hot bleed" after my first session on Saturday...Other than that, I am truly at a loss for getting a firm brake lever. Any help/guidance is greatly appreciated.

 

[ninjamansc]

I've run into the same problem a couple times. The best solution I've found is to get a mighty-vac. It's a handheld vacuum pump designed for brake bleeding.
Hook a tube to the bleeder screw on the caliper (longest flowpath from MC), then bleed a little so there's fluid in the tube.
Dip the tube into the bottle of brake fluid.
Hook up the mightyvac to the bleeder on the MC.
Open both bleeders, drawing fluid up using the pump.
Hope it works.

 

[dlockhart5x]

MBH328;60148 wrote: Is it possible/desirable to bleed the banjo bolt on a master cylinder that already has a bleed screw?


1) Pump brake lever ~10 times and hold
2) Loosen banjo bolt 1/4 turn
3) Let brake fluid ooze/shoot out of the bolt into a catch-tray while holding lever
4) Tighten banjo bolt to Galfer torque spec and release lever
5) Re-Bleed entire system
.

:agree:
Often that will do the trick.

Other possible methods/ things to try.

Pull a caliper and pump the lever so the pistons move out. (not out of their bore, and this is a good time to clean them with a friends tooth brush and some soapy water)

Loosen the bleed screw and use your fingers to push each piston back in. If you know where the fluid ports are in the caliper, you can hold it so they are "up" as you do this.

Another option

pull the whole system and set it on a work bench and elevate the calipers so you are pumping any trapped air up. It takes some creative clamping to hold everything, but it does work.


good luck

 

[krw]

Bleeding the banjo may do it, this is a common place for air to get trapped. Before you do that, I would tap the calipers with a rubber mallet and wiggle the hoses. Then, let it sit for a little bit and repeat. This will get the air up by the banjo, so when you bleed it, it comes right out. The other important thing is only to crack open the banjo, don't loosen it too much.

 

[Meat]

Zip tie-ing the brake lever back over night is a very common way to firm up your brakes.

It works wonders.

 

[beac83]

+1 on the Mighty-Vac. That will clear lines from MC to calipers. For air bubbles in MC/reservoir line, you'll need to so some manipulation on the MC to get the air bubble to rise.

I had a similar issue - air bubble trapped in/near the MC. I took the MC and reservoir off the clip on and positioned it so that the air bubble could travel up towards the reservoir. After 10 mins or so, I squeezed on the reservoir hose until the air bubble came up into the reservoir. Problem solved. Look for where the highest point on the MC is. If it's not the bleeder, then you can't fully bleed with the bleeder. Move the position so that the air travels up - either to the bleeder or the reservoir.

 

[MBH328]

Thanks for the tips, guys. I will be trying an assortment of these techniques tonight, hopefully I'm successful.

Has anyone ever tried a hot bleed? I read about it in an article on the Turn One Racing website. I figured I would give it a shot after my first session tomorrow, since I'll be going easy on the brakes at that time anyways (please see my previous demonstration of idiocy regarding taking a power sander to my front rotors:banghead.

 

[One Slow RC51]

I would think twice about the hot bleed. If you have air/moisture in there you may get vapor lock and dump the front.