Did you put in a new water pump? I never ever use a used water pump. I had a TA and a Caprice that both had water pump replacements that were from Vatozone and in months both pumps started overheating. I got frustrated and sold both cars. The guy that bought the first one a day later told me I had bad waterpump. Same thing on the caprice. Also once the seals are wet with water and antifreeze and then dry out they will die.