When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
If you let the master cylinder go dry, you should bench bleed it, and burp the air out of the ports when you connect the lines. You should not see any bubbles coming up in the reservoir if the master cylinder is bled correctly.
As already mentioned, make sure the bleeder valves are at the top or you will never get all the air out.
I bled my whole system and replaced the master cylinder with less than a quart of brake fluid.
Have you looked at the base of the master cylinder to see if there is any fluid running down the front of the booster?