my 2004 g35 temp gauge is running really speratic. Temp rises really fast then drops. As it rises i lose all heat in my car and then returns for a short time as the temp falls falls. I just replaced my thermostat so I know that isnt the issue but I did notice that the water return hose and rad cap were cold at opperating temp and the radiator hose felt like it had no pressure any suggestions?[/SIZE]

 

There is air in your system. Burp the coolant system and you will be warm again.

 

http://crackaddict.com/~flynn/howtos...amco.howto.htm