98 Honda CRV, Overheating randomly what is the cause?

Hi, I have a 1998 Honda CRV that tends to overheat randomly (after an hour or so of driving) and go back down to normal. I replaced the thermostat and the problem still persists. We also checked the water levels and it does not seem to loose any water. What could be the cause?

Read more: 98 Honda CRV, Overheating randomly what is the cause?