Hello Fellas, I have a 2006 V6 Frontier that I recently picked up. The chassis has 240k and the motor has 90k. I'm having an issue on hill climbs, the truck reaches the indentation on the top of temp gauge and wont pass 4500 RPM at that level. I replaced the thermostat but it still does this. When I was trying to burp the system coolant was consistently rising and flowing over the top of the funnel, when I search on this subject it seems to lead to compression in the coolant system, pointing at a head gasket. However the truck runs great everywhere else, no white smoke, no murky oil, and no other signs of failure. Around town and on highway runs perfect, only over heats after about 15 minutes of hill climbs, any ideas?