First things first, I searched and even posted in relevent thread to no reply.

I have an 03' Enthusiast with approx. 90K miles. When it is hot outside, the a/c is running, and I'm stopped in traffic, the car begins to overheat. As soon as I start moving again, the temp lowers to normal. In the same conditions without the a/c running, the car does not overheat.

I checked the fluid after the first time and overflow was near empty. I added water and let run until air bubbles stopped. Two weeks later it did it again. I added fluid and could not find signs of any leak.

Additionally, when the a/c is running, it makes an odd noise that coincides with the engine RPM's and can only be heard with windows up and below 3K RPM's.

About a year ago the radiator busted and had it replaced under warranty. Since then, I've had no problems until recently.

You guys have any idea what it may be, where I should look, or what I should do? Any help is appreciated!

 

I know you live in FL but try running your heater on full once in a while to get the fluid through your heater core, you could have an air pocket in there.

 

Both times the car began to run hot I immediately switched the heater on and ran for at least 10 minutes. Haven't done so since adding more water though.

 

might be your thermostat or fan

 

Are your fans coming on?

 

Sounds like what Chris said are both fans coming on when you turn on the ac?

 

+1

Fans giving out are a very common prob with the Z and Maximas. Even if you hear them kick on make sure both are rotating.

Other possibilities:

Thermostat stuck open/closed
Air pocket in coolant system
Coolant leak
Low coolant

 

I checked both fans at time of first occurance and they both kicked on. I still hear them turn on however I'll visually check to make certain.

I'll check the fluid level when I get home to see if I've lost any additional fluid and relieve the air bubbles should they exist.

This may or may not be a dumb question, but does the coolant fluid circulate differently when the a/c is running?

 

No it dosent and only real thing thats diff is both fans kick on and not just the 1 fan.

 

Yup, what chris said, check that your fans are coming on. With the A/C running they should both be on, also while your in there make sure there isn't some kind of debris blocking your radiator or anything like that.

No, the coolant won't circulate any differently when the A/C is on, when the heater is on it will flow through the heater core, which is why it's imperative to run it full hot when you are refilling and bleeding air out of the cooling system.

It's possible you could have an air bubble, although I'm not sure why it would only present itself with the A/C running.

 

You ever figure this out?

 

Sorry for the delay. Both fans are operating correctly and found no visible debris blocking the radiator. I did not know that I should be running the heater while getting rid of air bubbles so I'll tackle that this morning.

 

If you try to get all the bubbles out - and you still overheat..

My vote is the thermostat. I replaced mine recently and I havent overheated since. same symptoms as yours and I have an 05 with less miles.. the inside of my thermostat was just old...might be another option for you..

 

Update: I filled up the overflow tank to the max level (it was low) and ran the heater simultaneously. The heater barely blew warm air. Ran for 5-10 minutes during which air bubbles could be seen in overflow tank. Turned on a/c to max cold & speed and ran for 10-15 minutes. During that time only the passenger side fan came on and the engine temperature never raised. I then turned the heater back on and ran for 5 minutes. The passenger fan never cut off and it still didn't blow warm or hot air nor did the engine temperature raise.

 

You've got to get it to blow hot before you can be sure all the air is out.

 

A big plus one as if you do not have hot heat at idle you still have air in the system.

 

Update:

Car recently starting overheating again. Pulled over and found overflow tank spewing a bit. So enough was enough. Went to dealer and bought thermostat and gasket.

Followed Nissans' directions (How-to)for replacing and have been bleeding air last two days. So far so good but haven't run a/c in 95 degree heat yet. Car doesn't blow hot air yet, but sure it will soon!

 

Also, its a good rule of thumb to have the car jacked up in the front when you are burping the system. This is because air naturally wants to travel to the highest point in the system while coolant is circulating, which should be the radiator and opened top fill to. This will direct all air bubbles to the radiator and out the top fill.

The air pockets love to hide in the heater core, as it is the far back of the system and there is no way out with heater off. This is why you MUST run the heater full blast while burping. The cool air when heater is on is because air pocket is blocking coolant from getting in the core, therefore core is not heating up properly. Once you get hot air, that means the core is getting proper amount of coolant flowing through it.

Also, be sure to top off your coolant again after burping, or you risk creating another air pocket. And for you test drive after burping, keep the heater full blast just to let the coolant circulate through the entire system and push remaining air pockets into the overflow tank.

 

GeauxLadyZ great advice!!

When I was filling it I had the front end up and the bleed valve open until fluid came out. Closed the bleeder valve and continued filling very, very slowly. I've since added fluid to the overflow tank twice and burped it a few times. Now I'm getting hot air coming through the a/c vents.

I'll continue checking levels after each drive for the next week or so just to be certain all air is out and no leaks present.

Thanks all for your help.

 

VQ can be a b!tch to get air out of the system... I guess I've been lucky, don't have a spill proof funnel and I never had big enough air pockets to overheat and was able to just keep topping off the overflow every few days until it quit going down.