overheathing problem =(

[napor]

I have done a lot of reseach and done a couple of things to my stock ka24de and still does it.... Everything started when my original radiator blew up... replaced radiator and then after a couple of weeks, my car started to over heat ever sence, it only does it when im driving it, after 10 minutes or so... it never does it when is idling even if i have it runing for a half hour, at first i will not have heat, and as the temp. gauge starts to go up, i get heat, then after 5 minutes or so my temperature gauge starts to come down to normal temp. at first i tough i had a bad thermostat, so i replace it 2 times, my first one was for a autozone one, still did the same things, so i replace it with a nissan one, still the same, i also noticed my lower hose never gets the same temperature as the upper hose, in any situation hot, cold normal running conditions, i bleed the system thinking is a buble in the system, that kinda stop it for a while like 2 or 3 weeks but then started again, i pressure tested it. i don't know what else i can do. please some help would be really apreciated. thanks guys