No basment heat

sidney r. bray

I installed 4 cast iron radiators in my basment several years ago in order to take some chill out of that area in the winter..I did not set up zone valves because I wasn't interested in attaining a set temperature..I originally did a two pipe design but when I didn't get heat switched to a one pipe design thinking it would be easier to move the heat through that system...I installed coin vents on the 90 deg elbows at the high points above the radiators near the floor joists and also on the radiators..I also put in boiler drain valves in-between the radiators high up along the joists. I can ball valve off the main level heat by throttling down those valves to try and force water through the basement but to no avail. I have an HE5 WM pumped on the return side, but no air separator device that's typical in new construction (my boiler is 1987). I even tried a circulator on the supply side for the basement loop but still no luck....Is there something simple I'm missing?? I never get air through the vents or boiler drain valves only water, but cool water.