Cooling system

Goodmorning! I have a Cirrus 99- 98500 miles. 4dr sedan. K here goes. Last year in the latter part of hot weather my car was overheating and mechanic checked with pressure gage an seen small pin hole in pipe, not rubber. Ok it was replaced. Conversacion when car was p/u by family member was that antifreeze was to be added. Message was not related to me and then came winter. First freezing weather came in and now car was starting to act up. She didnt want to start so I was told it was the battery ok I purchased a new battery, then 2 weeks go by and car wont start again Strauss mechanic told me it was the starter ok I change the starter. Now the weather is getting worst. The car starts to act up again. Now she wont move. White smoke is coming out. Ok I have car towed to mechanic which replaced pipe in the summer. He checks car and sees that in pipe on top where you take pressure cap off its all frozen. My engine is locked. I need a new engine! Ok engine is replaced. Now air conitioner dont work all summer. I visitmechanic and live with the heat in the car all summer.I have antifreee in container but see that where the pipe on top where pressure cap is there ppars no antifreeze and its muddy. Mechanic feels somethng is going on with antifreeze cause his clients seem to be having same problem with this muddy substance appearing. He cleans pipe and ask me to purchase new cap. Ok now just yesterday when I return home from work. I turn off car and I hear this gurgling noise I pop hood and the resvoir to hold antifreeze and boiling like crazy, engine is hot. Before I go and tell the mechanic where I want to put my foot, what do you think is the problem. I just paid off the car note and paid $1700 plus all other new parts to keep the car. Please help me get this rectified.