coolant issues

[94 E320]

I'm having problems with my 94 E320 regarding coolant. I had siphoned a litre of coolant from the expansion tank last summer due to rising temps as warmer weather approached, this winter I decided to reverse the process and extracted solution and added antifreeze. The trouble begins...temperatures continue to rise and fumbling for a solution I added more antifreeze, temperature soar, now I'm backing off and adding water, I can see a slight change, but there doesnt seem to be exchange between the radiator/block and the resevoir fluids. How do I get it (water) into the block if it won't circulate? Also, after a sustained drive with rising temps, the expansion (resevoir) tank is cool to the touch, and after a cap change the top hose to the radiator finally has pressure after driving. I'm at a loss and have purchased a replacement thermostat and gasket, but I've introduced so many variables, I don't know if that is the proper course or not, and, did I introduce air into the system, if so, after parking at a steep incline with the heater running full on, should the cap be on or off, or, bled after shutting off the motor? Help me please
E320