Greetings,
Long time lurker, first time poster. I purchased a 2003 Maxima SE early this fall and have repaired all the little issues with it and have been loving it! However, I'm having serious difficulty with the heat. What it is doing is blowing moderately warm air when set to full 90* Hot. After a 22 minute highway drive from work it is just starting to get the interior almost comfortable, but still on the cool side. The thermostat seems to be doing nicely as the coolant gets to 180+* within a few minutes and stays there. The ambient temp tonight was 8* and coolant was up to 180* by about the 8 minute mark and remained there for the rest of the drive. Yet the air never got hot or much more than mildly warm

I have bled the system for a very long time and never managed to get any air out - car on ramps, radiator cap shimmed open, coolant overflow attached like an IV, etc. The system does not leak any coolant. Also, the heater will start to blow cool to cold air at idle (classic sign of air in the syste, but YMMV)

Having daily'ed a 1995 Saturn SC2 (1.9l) and a 2004 Buick Lesabre (3.8l) I know that both of those vehicles will quite literally burn you out of the car if you set the heat to maximum on the same drive cycle, but the Maxima just isn't cutting it. Thank God for the heated steering wheel!

Any thoughts on what I need to do to fix this? Thanks in advance!

 

Maybe heater core clogged only... that is where the heat comes from.

 

I certainly hope that is not the case, the heater core looks extremely difficult to get to in this car. Unfortunately, that does make about the most sense.

 

Naturally, make certain that radiator is filled and fluid in overflow bottle, then feel the heater hoses to be certain that the supply hose is hot and the return the same. If return cooler, then the core is restricted, if same temp, not the core.

 

What is more often the problem is that there is air trapped in the cooling system. The heater core is the high point, so that is where the air stays. The thing to do is raise the front end a bit, 6 to 12 inches. With the engine cold, remove the radiator cap, then start the engine. Let it run until the engine warms up and the thermostat opens. This is when trapped air will escape. The air bubbles may make the coolant splash out, so don't have your face over the radiator filler neck. But do check that the top tank of the radiator does not become completely empty. Let the engine run for maybe another 5 minutes to get all the air out. Turn off the engine, fill the radiator completely (no air space) and put the cap on. Check that the expansion/overflow tank has coolant.

Since you have the auto climate controls, another possibility is that the controls are messed up. The auto climate controls use 4 (?) air temperature sensors. If one is bad, the controls won't work correctly. See page 43 in the link below on how to run the built in self diagnostic.

http://boredmder.com/FSMs/Nissan/Maxima/2003/HA.pdf

Notes:

If run at night or in a dimly lit garage, you will get error 25, Sunload sensor.
Section 3 of the test takes a while, so don't panic.
Section 5 displays the temperatures reported by the sensors, so have an idea of what the actual temperature is.

 

had the same problem, and the was air in the system, coolant tank had blockage ect.

 

You guys are awesome, thank you!

As to what turbonut said the return hose was significantly cooler than the supply at idle, of course air in the system could cause that too. I'll run the self diagnostic tonight and try bleeding it again too.

 

Well the self test passed each step with flying colors.

And the second bleeding attempt purged no air what-so-ever. Other than getting rather cold at idle I can live with it so for now I am going to investigate further in the summer when the weather is nice and not worry about this winter.

Thanks guys!

 

On a dodge v6 that wouldn't bleed by normal methods, I flushed the heater core (flush part irrelevant). Since the core was now full of flowing water, I had a friend reconnect the outlet hose, then I connected the inlet. Pinch the hoses before you remove them, so them and the block don't drain. The POS dodge now has perfect working heat!

VQs bleed easily, so idk how this hasn't been fixed, though. Park the **** on a steep incline and try again. You have to race the engine if the air is this stubborn.

 

I remember having a similar issue when I owned a jeep. I don't know if a maxima has blend doors like jeeps do but if so this is most likely your problem. The only other thing that it could be other than a clogged heater core is your blower motor.