So I flushed my cooling system today, and saw that I could spray water through my engine even though it was cold...

So I assume my thermostat is slightly stuck open ( it did not flow out very fast) could this be true? I run at perfect temp 180-190 and warmup within a few mins...

I also realized my car runs MUCH better with only water in cooling system (steady strong idle/startup) before it would fluctuate and start rough...(why could this be?) *I'm running pure water for a few days to clean out any crap*

Car is 00 Civic EX (D16Y8)

Any advice much appreciated!

 

My thermostat was bad. It would over heat and the coolant would overflow. They're cheap, i think around $50 USD. The idling could be many reasons. Any cels?

 

Don't run without anti-freeze - it provides a higher boiling point, prevents freezing, stops corrosion, and in some motors the water pump relies on it to lube the bearing.

At least throw a bottle of water wetter in there.

 

Oem Thermostats are like 15$ not 50. Your car cools better with water because water cools better then antifreeze. As far as it starting up and running better I don't think running water has anything to do with that. You do want to run some antifreeze tho because of its anti corrosion characteristics. And for the obvious reason of keeping your coolant from freezing. But you really only need a 50-50 mix adding more antifreeze actually lowers the cooling ability. You could run a lower percentage of antifreeze depending on the weather where you live and your elevation. It's best to use distilled water also. Hose water has minerals that can corrode. As far as some water pumps needing antifreeze to lube the bearing I'm pretty sure its to lubricate the seal. The bearings are sealed. I would go ahead and replace the thermostat. They should be replaced as preventative maintainance over time anyway.