One of the most common causes of overheating issues like you've described are air bubbles trapped in the coolant system. (yourmechanic.com)
Common sense and thinking ahead will allow you to avoid serious complications from overheating in your cat. (cathealth.com)
But more than once, instances of overheating in some houses made them uncomfortable and measures had to be taken to counteract the excess heat. (passivehouseplus.ie)