The engine thermostat stays at about 60-70% ish I think when the engine is ran for awile during the day (80F) outside.....during the mornings its 30-50%ish when I go to school.....I was told those are too high....so how often does the coolent have to be replaced, as far as we recall never has been changed.

 

theoredicly never... but http://www.baltimoremd.com/content/antifreeze.html

 

Not very often. Considering it's very easy and cheap, every few thousand miles (~10k?). But, your problem isn't your coolant.

Do this:

http://www.aaroncake.net/RX-7/cooling.htm

Then get back to us.