Coolant leak after thermostat install...
 

I installed the mugen thermostat today. Now I have a leak. Few questions.
1. Does the thermostat have to go in a certain way? Does it fit in? Or does it just have to be facing the right way?(doesnt matter which way it is turned)
2. Do I have to do a full coolant change? I didnt open any bleeder valves, just poured in coolant, is that it?
3. Where are the bleeder valves that must be open when changing the coolant?

never looked at the s2k's t-stat b4 but they do need to go in a certain direction. most cars they only fit in one direction.
where is the leak comming from? the t-stat area? did you replace the gasket?
did you scrape off the old gasket AND clean the mounting surface?
you dont need to flush your coolant but you mostlikely have a small air bubble in the system. get one of these

http://www.amazon.com/gp/product/B00063W9F...glance&n=228013

they work great!

The thermostat faces only one way and it also has a bleed hole that needs to be at the top. Read my "How To" on the coolant flush and you'll see the bleed points that must be opened and in what sequence this must be done. If you have a leak, you didn't seal it back up the way it's supposed to be.