RSOLVED-Thermostat stuck?

[mam4.6]

Well, I'm feeling a bit like a dunce! Cleaned the X up and let it set in the garage ever since it started acting up, since I wasn't about to change a T-stat and dual temp sensor in freezing temps. We've had mid 30 degree weather this week, so I decided to go for a drive and see how she's acting. VOILA..! Everything works as designed.

I get to thinking... Last fall not long after I picked up the X from my Indy after my prev maintenance, I developed a small leak in the coolant hose at the rear of the engine. Some coolant leaked out, I shortened the hose about an inch, added some distilled water, and kept trucking. I remembered all of this and decided to check my water/coolant ratio. Yep, it was only good till 5 degrees F! We've had quite a bit of sub-0 degree weather this winter. I thlnk my coolant would start to slush in the radiator, (since it only happened on the most frigid days) restricting fluid movement, thus causing it to overheat.

Now my question is, can i drain some fluid, and add coolant, or should I totally drain the whole system and refill, to know exactly what I got?