I have an 04 G35 coupe. A few weeks ago it started running hot so I replaced the thermostat. Still running hot. I had the system vacumed,flushed and still running hot. Iv'e bled the air out many times. Finally I replaced the thermostat with a OEM and it seemed to fix my problem. I have driven it 300 miles since and no problems. Then last night it starts to run hot again. I started it up this morning and no heat is coming out of the vents so I bleed the air out again and I instantly have heat. Is it air in the system? It did pass a head gasket test too. Any suggestions? Thanks

Muddkicker wrote:I have an 04 G35 coupe. A few weeks ago it started running hot so I replaced the thermostat. Still running hot. I had the system vacumed,flushed and still running hot. Iv'e bled the air out many times. Finally I replaced the thermostat with a OEM and it seemed to fix my problem. I have driven it 300 miles since and no problems. Then last night it starts to run hot again. I started it up this morning and no heat is coming out of the vents so I bleed the air out again and I instantly have heat. Is it air in the system? It did pass a head gasket test too. Any suggestions? Thanks

Could it be the radiator fan(s)? What about the radiator hoses? There could be a tiny crack/hole in one somewhere or one of them might be loose.