I have a 07 G35x (VQ35HR) and yesterday while driving on the highway my coolant temperature shot up to max (I didn't notice), check engine light came on and engine went limp. I pulled over and let the car cool down. I inspected around the car and there seems to be no leaks. The check engine light was solid and not flickering, so I drove it home slowly and letting the car cool down every time it went beyond the half way point on the temp gauge. Engine still sounds and runs fine, absolutely no weird noises. I pulled the code today and it was what I expected, P1217. I did notice however, I did lose a bit of coolant level in the overflow tank. (It was at max before now it's just a bit above min)

My next step is probably doing a coolant flush along with switching out the thermostat. Doing some research it seems like the thermostat is the likely culprit. To my knowledge the thermostat is located at the end of the lower radiator hose and there is also a smaller oil hose connected to it? If someone can confirm that'll be great. And anyone who has experienced this code it would be awesome if you can share your conclusion!

 

I would pressure test the system before starting any work just to verify you didn't screw up the head gasket from overheating.

Also check the fan to make sure it's actually turning on when the engine is up to temp, aux fan can be tested by turning on the AC, primary fan is triggered by the temp relay so the engine just needs to get up to temp (probably not the fan since it overheated at highway speeds).

Since you were low on fluid (might have just boiled off from overheating) I would refill the system and see if it STILL overheats, check for any leaking fluid, you may have just sprung a leak on a hose and bled out coolant thus causing the overheat.

Inspect the radiator (particularly between the AC condensor and the radiator) for debris that may be blocking airflow.

If those things check out and it still overheats then swap the thermostat since it's cheap and easy, the "oil line" you are referring to is actually another coolant line that goes to the oil cooler (liquid to liquid heat exchanger). It's one of the easier thermostats to replace of the hundreds of cars I've worked on over the years so... Get it up on jackstands and everything is very easily accessible. The FSM here shows the location of the t-stat housing and directions for removal/installation on page 22, good luck bleeding out the air, get a spill-free funnel and read up tips (search button ftw).

http://www.nicoclub.com/service-manu...7_G35_Sedan/co

 

Oh man thank you so much!!!! this is great!!!!! I really appreciate you taking your time to help me out! I'll let you know how it goes!

 

You can rent a block tester from AutoZone as well for like 20 bucks. It's a chemical test you put on top of the radiator that siphons in fumes. If it detects exhaust gases it changes colors and also let's you know if you need a new head gasket.

I would do both tests to be certain.

 

Thanks for the input guys!!! I finally got sometime to work on it today and I drained the radiator and pulled out the thermostat. With a new one I bought at auto value I put both of them into boiling water. To my relief the old one remained shut while the new one was wide open. Replacement will have to be next weekend as the thermostat I bought seems to be a bit lower quality, I'm going to wait until Nissan opens on Monday to get an OEM one.

As for the Head Gasket I'll see if my car runs fine after I slap back the new thermostat next week. From what I can tell starting my car up today it is completely fine. I ran the engine for about 10 minutes until it reached the operating temp and there was no weird sounds and the exhaust gases were as usual.

THANK YOU GUYS FOR THE INPUT!!! COULD NOT HAVE DONE WITH WITHOUT THE HELP