Ok, just bought an 04 G35 coupe 6 speed MT. Everything was great until I took it to have the radiator drained and filled to make sure it did not need to be back washed. Everything looked good! However, I no longer have heat, and the car will begin to over heat after about 10 min of hwy driving. I burped the lines thinking it was air in the system, I did this per every forum I could find. Finally I Thought the Thermostat was gone, so I put a new T-stat on it this morning. Same problem. Burped the lines again, added more coolant. Made a huge mess and still having the same problem. Took it back to the Mechanic and he burped the lines as well, added more coolant, and finally got some warm air going. But then drove for about 10 more min and the air went Ice cold again, and the car started to Run hot. I am hoping I did not just buy a car with a mystery problem! PLEASE HELP

 

Here is how hot the car was running just at idle with Heat full blast, and by heat I mean ice cold air! also would run all the way up to the first thick line before it hit the Danger zone!

 

yes, feel your lower radiator hose, you'll notice that its cold too. This means air is trapped by the thermostat and keeping it from opening up to circulate it properly. Also, air in the water pump making it cavitate and not cycle much i'm sure too.


Either way, a proper air bleed and you will be good.

Don't let the needed get too high.

If you have a Lisle spill free funnel this is the easiest/fastest way. If not, you will just need to let the car sit for about 5 min and use the burp valve at the back passenger side. Make sure to open slow...close it as soon as all the air has escaped. You may have to repeat this process of turning car on/heating/cooling/letting air out many times before it starts working but you will know you got it when the lower radiator hose is hot.

 

Make sure that you keep the overflow tank filled to MAX as well.

 

Thanks Willey! I have been investigating all day, and looks like that is what it is going to take. Apparently this car is a PITA to get all the air out of the lines. But I will keep working on it. and I never let it heat past the first think line. Any time that happened I shut it off and let it cool for 10 - 15 min then limped the rest of the way to the driveway. Just to make sure I fully understand the burping process. Let the car idle to operating temp (heat full blast), turn it off, let it cool for about 5 min, then open up the bleed valve until air stops coming out, and repeat as needed. Every time use the Lisle spill free funnel to make sure no fluid is lost on the front end, and add extra fluid as needed.

 

Ok, I bleed the coolant system for about 4 hours, and could not get the thing to work right. I might have bought a faulty T-stat. I will order one from Nissan next time, but the reason I believe this is that when I was burping the system the fluid in the rad that I had a funnel in would not churn. To me is looks like the T-stat is not opening properly, but I have a mechanic looking at it to see if he can figure out what is up...It is a complete mystery to me.

 

Finally got it working. Tested the old T-stat, and nothing was wrong with it. The new one was a piece of crap so I took it back, got my money back, and the world is right again! I figure after they initially did the radiator service the guy left air in the system. Then I put on a broken T-stat. Now no air in the system. and the T-stat works great!