My engine was running a little warmer than usual so thought I would flush and fill the coolant system. Was going to replace the thermostat but the lower real bolt on the housing is impossible to reach - must have to remove a bunch of stuff from the front of the motor. So not doing that now unfortunately by here's my problem. I drained my radiator and pulled the lower radiator hose to make sure I drained most of the coolant from the radiator. I filled the coolant reservoir and let the engine run until I thought the thermostat opened then put the cap on. Engine now overheats and aux fan runs once the temp builds. I loosen the cap on the coolant reservoir and allow it to empty itself. Putr the cap back on and run for about 3 minutes down the road and once again the temp heads toward 120. Shut it off and repeat the procedure. I am doing something wrong with filling the system. I seem to have created an air lock of some sort. Would appreciate any tips from anyone who can set me straight on the proper process to follow. Very grateful for any info!