Today I noticed something weird:

When I am at idle, especially at a long stop light or something similar, the heater does not make hot air through the vents, even with the temp turned all the way to 90 and the fan cranking as fast as it will go.

But as soon as I start reving the engine, or simply start moving fast, the cool air turns hot pretty quickly.

Then when I come to a stop and it idles for a bit, it goes cold again.

Please note that all of this occurs when the engine is plenty warm. Does anyone have any suggestions or any experience with this? I just hope it isn't expensive to fix.

On a side note, the A/C definitely works fine. There just seems to be something preventing hot air from the vents when the engine idles at low RPM.

The car is a 2006 G35 Sedan with 48K, and It actualy received a new engine about 700-miles ago due to a con-rod bearing defect....

 

What is the outside temperature when this happens?

 

I knew i forgot something...

I live in Orange County, CA, and it was 53 degrees today when I noticed it.

 

You have air in the cooling system. There is a bleeder screw near the firewall on the passenger side. Make sure your coolant overflow tank it topped off too.

But since you have a new engine installed, take it back and have them do it right.

 

Mine does this too.... I wish their was a DIY how to fix it lol I don't understand peoples directions haha

 

^ the bleeder screw? I Believe bythabay has a video on it

 

Yes, here's the video

 

So basically, you just turn the little screw to relieve air?

 

^ Yep but I believe the car needs to be on, and coolant will spill, so you probrally going to have to buy for 8bucks a premixed bottle.

https://g35driver.com/forums/engine-...loud-boom.html