Heater blows cold air at stop lights
 

I got a question about the heater in my 03 sedan. Now that is starting to get really cold in Michigan, I noticed that if I am stopped at a light, and if the heat fan level is high that the car blows cold air. Now I know it is easier for the heater and AC to work while you are driving, but I don't remember it being this bad last year. Has anybody else experienced this?

My heater blows very hot and it's been pretty cold here this past week. It sounds like you may have air in your cooling system.

^+1 on air in the cooling system. Do you hear the sound of running water when you rev the motor?

Crap...I do hear the sound of running water! What is the fix? Is it expensive?

EASIEST FIX EVER!!!! :)

First I topped up to coolant resevoir. I then let the car heat up to normal operating temperatures.

I used the bleeding screw behind the engine, and was able to get some air out of the system and get heat when idling.

I also had to do a second step, as I started to get some more heat then before the 'burp' but it was not enough and did not seem correct.

The other step I did after opening up the bleeding screw and letting the coolant 'burp, was take the rad cap off, let the temp raise to normal operating temperatures and leave the car to idle for about 20 min. I then slowly revved the car up to about 4500, and back down, doing this a few times - and the heat noticably increased and stayed hot at idle.

Its been 2 weeks since I have done this - and it has remained consistant!

MORE INFO:

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

It's no big deal. If you haven't changed the coolant in 60k miles, you should go ahead and do it while you do this. There is an air relief on one of the hoses towards the back of the engine near the battery. Watch the video bythebay put up on infinitihelp.com on the coolant change service. If you don't want to change the coolant, just unscrew the relief add more coolant to the reservoir and wait for a little coolant to spill out of the relief. That should mean there is no more room for air in the system. Normally, air gets into the system when the coolant reservoir goes empty and air gets sucked in instead of coolant. Good luck, it's a free fix!

So apparently RATED_G beat me to it. He's doing the same thing.

Thanks for the help.

I find it much more effective to just keep the car running at idle and burp the system via the air relief valve every couple min. Paying attention to the heat and making sure the temp doesn't rise too high. In between air burping I rev the engine like above.

!!IMPORTANT EDIT " My car is not overheating at all ---- " My car is driving and functioning great - no temperature rise/drop.


Heat was coming out of the vents cold only when I was idle - As long as I am driving the car around the heat comes out great- it's cranking hot!

Once I idle the car it begins to cool very slowly until its all cold again....about (5 to 10 minutes)

Took the car into Infiniti Dealer - Paid 125$ for flush/fill coolant and 65$ for a full inspection of the vehicle.

They do the flush/fill heat was working fine after I left.

48.Hours Later -- Heat is coming out cold again when I idle - but if I keep driving the heat stays hot!

I have been checking for leaks of coolant around the engine/block/hoses/etc.

Nothing found to be leaking? I hear the "Water gulping" from inside the car while I am starting to begin to drive. I just bought a thermostat I have not installed it yet- however I don't think that is going to fix it anyway - but that is why I am here.

What have all you found to be happening after this? I have searched the forums and found a few good threads and will continue to post this and read more.

Thank you all for any help or time you give me -:confused2:

Joe

Take it back to your dealer. There is still air in your system. They should re do the work again for free since they didnt get it all the first time...or you can follow the advice above to get rid of the air. Make sure that your overflow is to the MAX line as well.

UNLESS you have a heater core leaking...which I haven't heard of anyone with a G35 and a leaking heater core yet...so its not very likely.

Thanks for the response
 

:icon17:

Yeah I don't see any coolant or smell any coolant inside the car.

I have not seen any puddling of any coolant outside the car on the driveway or where I park the car.

The inside of the bay is so clean that I could eat breakfast on the plastic cover of the block.

I really do hope that this turns out to be the issue -

Ill be sure to let everyone know what happens if monday this is solved.
Thank you for responding TollBoothWilly. :thewave:

Take it back to the dealer and say "the heat is cold now" and leave it at that. I wouldn't even say it was doing this previously. See what they say there.


If it's not air in the system, my next step would be to replace the thermostat.

Water gulping...its air inside the heater core

Heater Core...
 

Well if it is in the heater core is it flushed with the entire system also?

What could create the air pocket? What is it that I am doing wrong? The car was sitting for a while before I bought it and no one drove it at all.

My car did this when I first bought it too. Just burp the system using the bleeder valve. I wouldn't pay anybody another dollar. It seriously takes less than 30 minutes and the problem will go away.