A few days ago, my girlfriends neon over heated on the way to work. I let it cool off, filled it up with coolant and drove it home (about 16 miles) and it ran fine and didn't over heat.

After getting home I was changing the thermostat and realized the water pump was leaking, so I changed it. Got it back together, went for a test drive today about 5 miles, and it is now over heating again. I made sure the thermostat was in the right way and the tank is full of coolant.

Kind of stumped, any ideas?

 

Did you bleed the system of air?..

 

Yes I did. I believe I was sold a bad thermostat.... I pulled the center out of the old one, put it in and took the same test drive and didn't have any issues this time around..

 

What center did you pull out of the old one? I believe that center you mean is the thermostat. You pulled it out of the thermostat housing.

To check if your new thermostat work, you put it in a bucket of hot water. If you don't see it open by any (in a few minutes), then it isn't working.

Not every thermostat open at the same temperature, so you have to buy one that meet the specs of your car.

 

I think your knock sensor will need to be replaced soon too.

At least that is what happened to my car. I had to replaced it.
They say: usually when a car is overheated, the knock sensor go out after.

 

Haven't heard that one before. My car overheated when my radiator blew out not too long ago and the thing has been running just fine since.