<VV> Dual or single master cylinder

[NicolCS at aol.com]

<snip>JVHRoberts at aol.com wrote:
... leave only one bleeder open on a Fiero, and the pedal goes damn near to 
the floor! ...
<unsnip>

Someone correct me if I'm wrong (Patrick / AngryP?) but...  If you have one 
bleeder open, the pedal will sink to the floor - this is how we bleed brakes.  
If you mash the pedal and one circuit is out, the combination valve will 
detect the difference in F/R pressure and the shuttle valve will move to block the 
offending circuit and turn on the "brake" light. Takes the reverse to recenter 
the shuttle (some have a centering button on the end).  (Some later 
combination valves automatically isolate the circuits and you have to use a special 
tool on the end-button to allow bleeding.)  All dual master cylinders have two 
pumps and two outlets.  The difference is in the combination valves.  For our 
cars, if one circuit is out, mash the pedal to seal-off the bad circuit and stop 
using 1/2 the brake system.  
Craig Nicol