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4/03/2013 1:22 PM  #1


Bench bleeding a new master cylinder.....

I have never bench bled a master cylinder before. Could someone walk me through how to do it. Why? And any tips or tricks?  Thank y'all. 


1966 Mustang Fastback K-Code,289,T-5, 9-inch rear with 3.50 gears.
 

4/03/2013 3:11 PM  #2


Re: Bench bleeding a new master cylinder.....

T. this is probably when I find out I've been doing it wrong but I have 2 short pieces of brake line with fittings that I thread into the MC outlets and redirect them back into the bowl. With the MC in the bench vise I use a large screwdriver to pump the MC until it is free of air.


"anyone that stops learning is old, whether at twenty or eighty"Henry Ford
 

4/03/2013 3:31 PM  #3


Re: Bench bleeding a new master cylinder.....

Thanks Billy. And thanks to MS for the quick shipping and great instruction in the box on how to bench bleed. Guess I should always OPEN the package first and look inside!!!!


1966 Mustang Fastback K-Code,289,T-5, 9-inch rear with 3.50 gears.
     Thread Starter
 

4/03/2013 3:43 PM  #4


Re: Bench bleeding a new master cylinder.....

So when you unscrew the two fittings to install new lines how do you keep air from getting back into the MC? I just did this last night on my new MC and fluid came out when I unscrewed it. Of course there was fluid in the lines running to the top, I just want to know if air can get back in while installing new lines.
BTW Eastwoods flare tool and line bender FREAKING ROCK!!! I have never made brake lines before and I was snapping out some good stuff without any issues.

 

4/03/2013 3:52 PM  #5


Re: Bench bleeding a new master cylinder.....

I install the cover and leave the bleeding lines in until I'm ready to connect the lines on the car. If anything you will get some fluid dripping out but no air in.


"anyone that stops learning is old, whether at twenty or eighty"Henry Ford
 

4/03/2013 3:56 PM  #6


Re: Bench bleeding a new master cylinder.....

Thanks BillyC, That is where I am at right now. I have the lines plugged up and waiting for me to build the rest of the brake lines.

 

4/03/2013 5:33 PM  #7


Re: Bench bleeding a new master cylinder.....

Tmac, here's my method. Usually new M/Cs come with rubber plugs at line fittings, simply hold plugs in and GENTLY push in piston using small strokes until all air is gone from resivour fluid return holes and no air is presant at rubber plugs. You lose a little fluid, just use rag to soak up excess
Howard

 

4/03/2013 8:07 PM  #8


Re: Bench bleeding a new master cylinder.....

I had some old plastic tubing laying around that I used.


 

4/03/2013 10:00 PM  #9


Re: Bench bleeding a new master cylinder.....

This is the new Disc/Disc Master Cylinder with proportioning Valve. I am about 1/4 inch from the shock tower. These are my first attempts at making brake lines.

 

4/04/2013 8:31 AM  #10


Re: Bench bleeding a new master cylinder.....

Ok... please don't flame me for this, but I always "bench bleed" a master cylinder in the car.

I still run the hoses back into the master cylinder bowls.  The only difference is that I use the brake pedal to pump the master cylinder instead of a screwdriver.  You just have to be careful to do slow short strokes with the pedal.

I have done this many times over the years, always with good results.  The main reason I like it is because you don't have to worry about spilling brake fluid on your paint while installing the master cylinder (and because I don't have a good vice to clamp a master cylinder into).
 

 

4/04/2013 8:40 AM  #11


Re: Bench bleeding a new master cylinder.....

Michael H. wrote:

I still run the hoses back into the master cylinder bowls.  The only difference is that I use the brake pedal to pump the master cylinder instead of a screwdriver.  You just have to be careful to do slow short strokes with the pedal.

Nothing wrong with that method.  I've seen it and have done that my self.  Just depends on how much room I have to work with.  Have to bleed the brakes this weekend after I get the rest of my install done.

 

4/04/2013 8:44 AM  #12


Re: Bench bleeding a new master cylinder.....

Mochaman - hard to tell from the picture perspective but it looks like your lines are going pretty high after going under the master.  Those apparent loops will potentially catch air that you can't bleed out.  Might be just the picture though...

 

4/04/2013 12:03 PM  #13


Re: Bench bleeding a new master cylinder.....

I agree with Gary, Mochaman.  That prop valve on top of the booster might cause trouble trapping air since it is higher than the fluid level


Money you enjoy wasting is NOT wasted money... unless your wife finds out.
 

4/04/2013 8:52 PM  #14


Re: Bench bleeding a new master cylinder.....

Well since this is my first time building a brake system from scratch. I never thought of air trapping above the MC. The bracket the Prop Valve is attached would only fit in this position because of the lack of room. Bubble popped on the good job.  Back to the drawing board.

 

Board footera


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