when the calliper is bolted to a sierra they are right at the top of the disc, but on my escort they drop back a bit causing the bleed nipple to be in the wrong position so the air goes to the highest point in the calliper where the nipple was. The only way to get the air out was to raise the calliper unbolted into its normal position open the nipple and release the air in the system, taking care not to damage brake pipe.
Hope this helps