If it pumps in air ...
like you never get the bubbles out of your bleed bottle clear hose ..
the MC is toast.

you can also have internal leaking, chamber to chamber ..
resulting in low pedal and poor brake performance . 

as I mentioned recently ..
there was a Diesel Westy I worked on that had iffy brake action.
First I got the wheel brakes  pretty straightened out ..
but  it still   seemed like 'booster' ......or MC,  or both.

new MC made a ton of difference. The brakes on that van finally started acting right. 
I only use good german ones. 

Scott
turbovans 

  ----- Original Message ----- 
  From: Jeff Lincoln 
  To: Scott Daniel - Turbovans 
  Cc: vanagon@gerry.vanagon.com 
  Sent: Wednesday, November 09, 2011 7:55 PM
  Subject: Re: Bleeding brakes - 1.9 - questions

  Yes manual - yep all the way to the floor. 

  So is there a way to test the MC to be sure?

  -- 
  Thanks,

  Jeff
  '85 GL (Gertie)
  '90 Carat (Grover - the noble parts donor) 
  '78 Bus (Melissa) Patty's Bus