I just got an '83 Venture, and the brake lever seemed pretty soft, so I checked the fluid in the reservoir at the front brake lever (it was full).  I decided to bleed the brakes, and I started with the right front caliper, which bled as it was supposed to, and started giving a little more pressure to the brake lever.  So I proceeded to the left front caliper, and it won't bleed at all.  Do I need to use a vacuum bleeder on this?  And I did some searching on this forum, and someone mentioned the back brake line is connected to the front brake line.  Is this true?  I've never had such a time bleeding a brake caliper before.