My original thermostat on my 2005 Coupe was stuck 1/2 open so the car was heating up to the point where both fans would come on high and never go off again. I hooked the computer up and it was running 210-216. I replaced it with a thermostat from O'Reilly that was a Murray brand. It claimed to meat all OEM specs but it looked like the opening was a bit smaller. I verified that it worked in a pot of hot water. After I installed it the car acted about the same as before. During cooler weather it would run hot and the fans would come on (fans wouldn't make the temp come down at all) and during warm weather it would run about 190-200. The only thing that would make the temp come down would be putting in in N and revving the engine.

I figured it must be that thermostat opening being undersized. So I went to Advance and their thermostat is a Stant, but it was obviously exactly like the original Nissan thermostat. I installed it and now in cool weather the car runs 185 and if I let it sit and warm up until the fan comes on low, the temp quickly drops 15 degrees and the fan goes off (like it should).

I just wanted to let everyone know to stay away from the Murray thermostats from Oreilly...at least for this car.

 

It might not be the thermostat, did you burp your cooling correctly after installing the thermostat? If you didn't this will cause your temps to go up.

 

It was burped. I spent several hours meticulously burping it by heating and cooling cycles with the front of the car raised and the rear plug removed from the hose. Also, I drove the car for 4 weeks and the coolant never dropped (after I successfully got all of the air out). And it continued to overheat in cool weather (but not in warm weather).

Anyway, after the first initial fill/burp with the Nissan thermostat, it was not overheating and the coolant WAS a little low. Besides that, I measure the exact amount of coolant that comes out (within an ounce) and know exactly how much I need to put in to get it back the where it was.

It was the thermostat...but if you ever need one just pay for shipping and the Murray is yours.