I just got my 2006 350z with 45k miles on it two weeks ago. Everything has been working fine untiil one day I drove it for about 5 or 6 minutes and my radiator cap blew off. I replaced the cap and then noticed my temperature gauge has been all the way up so I pulled out my thermostat and noticed it had some wear on it that suggested that it was sticking. So I replaced that, and now the temperature gauge will go all the way up, and then it will drop down to regular temperature and go back up, and down, and up and down/ (This happens within seconds almost) I'm not sure what to do or where to look now. My mechanic was saying theres a possible chance that it has a blown head gasket? Im really puzzled on what it could be, has anyone had this problem? Or can push me in the right direction on what to check next?

Thank you
Anthony

 

You need to bleed the cooling system better, you have a lot of air in it.

 

I will do this tomorrow. Do you think thats whats causing my temperature gauge to rise and drop so dramatically?

 

Well, believe it or not, I believe I have fixed the problem thanks to terrasmak. I bled the cooling system fully and took it for a quick 15 minute test drive (All the time I had to drive unfortunatly) and the temperature stayed constant. Also my heater blew hot air which means that I've purged the air. Thanks !
Anthony

 

Yep. Apparently, bleeding air out of these cars is a major pain and the directions have to be followed EXACTLY.