my 2 cents...
1.Check to make sure you have all the air out of the cooling system.
2.Check the fan to ensure its engaging.
3.Do you have the plastic style waterpump or metal style? Could be a
4. sensor could be bad also causing the gauge to show in normal and
not the actual reading.
5. check hoses to ensure they are not leaking.
6. did you place the thermostat in the right way. Meaning not upside
down. not trying to insult your intelligence.
7. Radiator leaking