Nissan Repair: Overheating, antifreeze leak, 2 cooling fans

Question
QUESTION: I have a 99 pathfinder le which has recently started to overheat.  It usually only does it on very hot days in stop and go traffic with the AC on.  I will turn off the AC and the temp gauge will drop quickly.  I checked the coolant and the overflow bottle was empty.  I topped it of with 50/50.  I then checked the radiator cap, which was bad and so I replaced that.  It is better, but still not fixed.  There is no steaming or bubbling from the radiator when running.  I suspect that my culprit is a small antifreeze leak on a part right under the throttle controls.  I think the part is the fast idle plunger.  I noticed this leak approx. a year ago, and it hasnt seemed to get any worse, but now it does look a little worse.  Do you think that this is my problem, and if so, how hard and expensive is this part to replace?  Thanks for your help.

ANSWER: Hi Shane -

If I am not mistaken, you have 2 cooling fans for the radiator. One comes on with the A/C for additional cooling, and the other goes on when the engine reaches a certain temperature. I suspect the latter is not working, since with the A/C on, the engine runs cooler, because at least on fan is on.

Best way to check this is to get a circuit light tester, 12V. Get the engine to operating temperature and check the terminal that goes to the fan for power. If there is power, then replace the fan motor. If not, then it could be the following:
Fuse
Thermostat
Fan switch
Cooling fan relay
This is in the order of probablity.

Hope this helps -
aloha
calvin


---------- FOLLOW-UP ----------

QUESTION: Thanks Calvin for the response. I only have 1 fan on my pathfinder.  I have observed the fan and I it is working.  I also hear the relay click when I turn on the AC.  I did replace the fast idle thermal element which took care of the leak and seemed to make my problem a bit better.  I took a 200 mile road trip yesterday and it seemed to run beautifully.  However, today, in the heat of the day and stop and go traffic, after about 30 minutes the temp gauge started to rise again.  any other thoughts?

Answer
HI Shane -

Have you checked your thermostat? Run the car til operating temperature, and feel the upper hose as compared to the lower hose. If the lower hose is substantially cooler, than it could be the thermostat.

The radiator core could be plugged. You seem to have trouble only when the car is running a bit, so a good radiator back flush could be in order.

Hope this helps -
aloha
calvin