[6pack] TR-6 Master Cylinder Woes

[Bill Wellbaum]

My M/C began leaking onto the servo.  I ordered a replacement from Moss, bench
bled it and bolted it on.  On bleeding the brakes, beginning at the right rear
wheel, the rear brakes bled cleanly--with minimal bubbles.  Bleeding the two
front brakes resulted in nothing more than big bubbles.  I bench bled the M/C
in situ again and re-bled the brakes--twice.  Bubble free fluid in the rear
system, big bubbles in front.
I returned the unit and had them send me another.  Bench bled on the car.
Same results.  Almost bubble free in the rear, big bubbles in front.  This is
not my first rodeo and having owned this particular car since 1994 I'm
confident I know how to bleed brakes.  Any suggestions on what could be
happening?  Two defective master cylinders in a row?  Both allowing air into
the front system?  Note:  I just checked the unit for leaks and there are
none.  The unit is dry top, bottom, and sides.
Suggestions please.

Bill Wellbaum
Las Vegas