under-heating problem?

[brycerxer]

This one has me scratchin my head: I had a coolant leak on my SE (the hose from the firewall that goes to the driver's side of the engine was leaking). After fixing the leak by cutting an inch or so off the bloated end of that hose and re-attaching, I flushed the system with a garden hose at the top of the radiator with the engine plug removed till it ran clear (lots of crud came out). I also checked the connection at the temp sensor before refilling w/ 50/50, bleeding, etc.

All is well, almost -no leaks, remove all the air bubbles etc. However, the temp gauge on the dash doesn't go nearly as high as it did before. It used to go to a straight down position after full warm up. Now it barely goes beyond the second of the two lines on the cold side, then gets even colder as I drive it.

I'm thinking replace the thermostat first. I hesitate to think its the temp sensor since it worked fine before. What do you guys think? Has anyone else come across this before?