Replaced the Crytotek 100 Poly Glycol in my home heating system. Completely drained the system. Pumped 30% mixture into my system with a transfer pump. Bled the air best I could. The system works and I have circulation but I am having to add small amounts of make up over the last couple of days. The system has an autofill plus backflow preventer but I have the autofill valved off because I do not want to dilute the glycol. Could the small amount of make up be needed to maintain pressure be a symptom of air working itself out through the air scoop? No leaks are obvious. Any thoughts would be appreciated.

I have a 4 flash issue with my day and night N8MSN0701412A1 I replaced the 165 degree limit switch because that's what the guy I had in today said was wrong. After I put in the new one got the same thing and the switch ohm'ed open any thoughts or ideas on what could be causing the over temp? Some background: new filter, all ducts and registers open, unit installed Oct 2013 but there was no Tennant in the unit last winter to confirm if this has been a continuing issue.