I know, year old thread, but relevant for my issue because I have the same problem as gasman had. 93 w/ABS I, rear mod first and then caliper, went fine.
Front modulator wouldn't give a drop, even with max vacuum ( usually use about 50% vac at the most ) so I did the calipers, went fine, three reservoirs each and back to the modulator still nothing. Thanks ahead for any ideas.
PS brakes felt fine before starting fluid change, same set-up as my RT, and now in the shop the front lever feels normal after fluid change.
And, seems funny to me that the input line from the lever/reservoir connects on the mod on the bottom port below the bleed nipple and the output line just above, and yet I can bleed the calipers, but not the nipple 20 mm above.
The bleed nipple threads into a reducing bushing or some sort. Anyone opened that up ?