2005 toyota prius Overheating

So I recently purchased a 2005 prius and I'm really loving it. However, I recently replaced the coolant flow position control valve due to a check engine light. After a day or so the light went off and no worries! Until the car began to over heat. I,ve replaced the coolant from the part replacement job, but what I believe is happening is the valve that I replaced contains air bubbles, or excess air pressure that is constantly pushing the valve cap right off causing it to overheat. I was just curious to see if anyone has advice on a fix, or maybe similar symptoms so I know my problem isnt so particular. Thank you.