what test did you do on the thermostat? it maybe stuck and only partially opening, you could simply need a new rad cap that holds proper pressure in the system as well, these are cheap i would swap a new cap on first. then change the thermostat next as this ould be another cheap and easy to change culprit outside that does it go down when you say turn the a/c on or off? how long does it take to warm up in the mornings after not driving all night? is the check engine light on, als what engine is it the 2.4l or 3.3?

 

The test was done by a mechanic. With the car full overheated, he spread water on the radiator and the temperature went down automatically. Radiator car seems quite new but I will change. I will also change the thermostat. The A/C is always on and it overheats when the day is really hot (I am in South Miami and I mean when temp is +90 degrees). At night or on grey rainy day it does not overheat. It takes like 30-45 minutes and app 10 miles, on US1 (I mean, hot, with traffic and stopping constantly) to overheat. Once in expressway, temp goes down. My Xterra is 3.3L. Thanks.

 

The test was done by a mechanic. With the car full overheated, he spread water on the radiator and the temperature went down automatically. Radiator car seems quite new but I will change. I will also change the thermostat. The A/C is always on and it overheats when the day is really hot (I am in South Miami and I mean when temp is +90 degrees). At night or on grey rainy day it does not overheat. It takes like 30-45 minutes and app 10 miles, on US1 (I mean, hot, with traffic and stopping constantly) to overheat. Once in expressway, temp goes down. My Xterra is 3.3L. Thanks.

 

Radiator Cap I meant

 

Have you tried to clean the radiator , it may help.

The truck should be cold, get your hose and from the inside spray out the radiator from top to bottom do not use a pressure washer as it may damage the fins. In addition then spray out the front. You should see a lot of dirt. Since you are in Miami you should see some bugs as well.

if you get a new radiator consider the SC version it is thicker and will better in your heat.

 

Huh, that's a little weird that it overheats in stop and go traffic, but cools off on the expressway. That would generally indicate fans aren't kicking on properly, or a lack of air flow from the fans, but as these fans aren't clutch driven, that shouldn't be the problem. Though, belt driven fans generally don't cool as well, these engines get hot as it is, so it could just be the climate you are in. I know a lot of people do some type of coolant line bypass down where the climate is a lot warmer. But I am from Michigan so I do not experience extreme temperatures that often. But like racks said above, i'd probably look into a new radiator, as you haven't mentioned changing that, and over time, the radiators ability to dissipate the heat deteriorates from corrosion and what not occurring inside.

Once last thing I'd suggest would be to bleed the air from the cooling system if the mechanic didn't already, that could also cause some issues but... not much else I could think of really.

 

 

Thanks.
I guess I will buy a new radiator (SC version?)and see coolants available for this hot weather. I will change thermostat as well.

 

One more thing:
if I turn the car on with the radiator cap off and the green coolant does not move or circulate, just stays put, does this mean the radiator is not working properly? or this is the thermostat that it is not opening?

 

I wonder if it could be the water pump or thermostat? I know alot cars when putting in fluid in you can see the circulation of the fluid? I'm still new with my xterra. I have some experience but mostly just to keep them running. I hope you get it figured out dude.

 

I changed radiator and thermostat and it is working good so far...

 

what you saw with no flow is usually indicitave of a stuck thermostat or bad water pump, but trhe pumps rarely fail unless the belt driving them does as well.

 

Hell yeah. I'm still new to this I just got mine about tworking ago. Did a little bit of trail ridding last night. So fare so good. I am glad you got it running.

 

what color coolant came out of the radiator when you took it out? did it have alot of rust color to it or was it nice and green?

 

Nice and green mostly

 

My 2004 did the same type of stuff in NC. Stop and go traffic was bad, and driving on the highway in direct sunlight would overheat if I was moving too fast (as it took more power, and would generate more heat). I had to stay around 60 MPH. AC would essentially be non-existent as everything got completely heat soaked. You've had good advice so far, but here are some other things to consider based on how I eliminated the issues.

1) Definitely get a radiator for a 3.3L supercharged Xterra, it drops right in.
2) Replaced thermostat and water pump (as I was due for timing belt anyway)
3) I installed an external transmission cooler ( mostly for transmission, but more heat rejected helps everything)
4) My AC condenser was pretty shoddy and I had a refrigerant leak. I replaced it and got it properly recharged -> I think this played a huge role. The AC system would generate heat in the condenser that couldn't be cooled, which would reduce the ability for the radiator to cool the engine (since they are located on top of each other).
5) Make sure there are no cracks in the fan shroud (plastic surrounding the fan)...as that can prevent the fan from pulling in cool air from outside.

I now have cold AC and no overheating even when 90+ degrees outside and stop and go traffic.