So I just purchased my 2005 infinity g35 coupe 6 speed from a local auction for a steal! It has 85,000 miles on it and I test drove it in the enclosed parking lot and it drove great. However on my return journey to my town (roughly an hour drive on the highway), about 15 minutes of driving had elapsed when the car shuddered, a check engine light came on, and I noticed my temperature gauge was all the way up to the 3/4 quarter mark, and the car would not accelerate, and I was eventually forced to pull over on the shoulder. Let me repeat this; the temperature needle was not all the way up on the gauge, just roughly 3/4's of the way up before the huge gap occurs. I had the car towed to a local shop and my town and here is where it gets interesting. They at first told me it was my thermostat after they had confirmed with me it was not a head gasket or anything like that as they had ran a test and everything came back clean and strong. Here we are two days later and they are informing me that I will need to replace my head gaskets as my car doesn't overheat while it is idling, but that it overheats very quickly (within roughly 4 minutes of driving at 45+mph) on a back road. They also mentioned that they bled the system roughly 4 times and the car still was overheating... I was wondering if I should have another shop give their diagnosis as this shop didn't provide me with a satisfying reason as to why they believed that the car needed to have the head gaskets replaced. Also, is there anything I should have done to the car when it goes to the shop that commonly causes these engines to overheat? I asked about the radiator and radiator cap and he said everything looks good. I really hope this isn't a head gasket situation and would appreciate any helpful input from you all!

 

Any shop that doesn't know these cars will most likely not be keen to the bleeding procedure. If you can't do it yourself (plenty of info on this site), I suggest taking it to a dealer. Normally I dont condone dealer visits, but for this issue I would. You probably still have air in the system, and these cars are notorious for being a PITA to bleed properly. 3/4 needle shouldn't blow your HG.

Also, just cuz the thermostat is new it doesn't mean its good. Thermostats and radiator caps come broken out of the box all the time. Let your car heat up, turn it off and feel the lower radiator hose. If it cold, your therm is still not opening

 

awesome thanks for the advise ill definitely try that tomorrow.. I'm just not willing to accept a head gasket for now (even though that's what it very well may be)

 

Just so you're aware, headgaskets on these cars are a particularly advanced job as well, so normally a used replacement motor is a better idea than getting the current one repaired if that's what it turns out to be.