thermostat problem

[Dean Machine]

Hey guys i used to run without a thermostat in but i recently put mine back in, not new it was used, and my car seems to overheat easily after being driven kinda hard..
I have got coolant in it. I am thinkin that maybe my thermostat isnt opening up? Is there anyway without having to take it out again that i can test if its opening?
Cheers guys

[ECU-MAN]

take it out and test it in boiling water.

[CRXDEL501]

take it out and test it in boiling water.

only way to do it.

[Dean Machine]

putting it in boiling water? how will i know its working

[destrukshn]

when it opens up?
what baffles me, is why didn't you just use a brand new one?

[vinnY]

did you bleed the system properly after reinstalling it?

[Dean Machine]

lol derr sorry..
good question lol