97 STS dumping coolaint once turned off?
 

Hello Caddy word, I am sad to say that I know squilch about cars. I love my STS but there is a huge problem that am having and was looking to pick your brains.
When I am driving my STS it leaks a little bit of radiator fluid. I think this is just a hole in a line, very fixable. But however when I turn my car turns off after driving home from work, it as if it spits out everything in the resivoir and then some. I believe it is spitting it out of the tube where excess coolant if it is over filled. The past few days I have been refilling my coolant almost every day. If i do not refill it every 2 days or so the car starts to overheat
Anyone run into this before? I had my water pump replaced a few months ago, am hoping it isnt that.