Cooling fan

[Scotty B]

When does the cooling fan kick on? I've heard mine kicking on recently and have never heard it before... It's fall in Wisconsin and been cooler, so I don't think ambient temp has anything to do with it. The temp gauge never gets above 1/2 and everything seems normal. I tested the relay with a multimeter and it is working correctly and the fans have been checked and verified to be kicking on high and low as they should... I am just curious if anyone else has the fan running under normal conditions? I have no idea why it would start running all of a sudden??

Thanks in advance for any input!!

[RX400h]

Have you been experiencing more traffic? Lengthy periods of slow or no motion could do it.

[Scotty B]

4 hours ago, RX400h said:

Have you been experiencing more traffic? Lengthy periods of slow or no motion could do it.

No, unfortunately... Same roads at the same time and it's even WAY cooler now than it was in August!! I am not sure why it kicks on, but I'm one of those weirdos that can't just shrug my shoulders and not worry about it, I need to find the source/reason for the fan running,lol.

[Bykfixer]

You are right to be alarmed. May be nothing to be worried about but your logic is sound.

My thought would be maybe the thermostat is not opening/closing like it once did so coolant may "seem" hotter at a sensor until normal flow resumes. 

[RX400h]

I assume you gave the overflow tank level and radiator a thorough look. I once parked over a piece of a cardboard box. When I started the car, the cardboard was sucked up against the radiator or its fan. Within a couple of blocks of driving, the temperature climbed quickly. I pulled over and quickly found the culprit.

[Scotty B]

So, as a follow up I drained the radiator and replaced the thermostat this morning and it solved my issue. Now, I didn't think it was going to because when I looked at the coolant, it appeared to be brand new! Clear, pink and not funny looking. When I got the thermostat out, I also was surprised to see that it also looked NEW!! After cleaning the mating surfaces and getting everything back together I was worried that it wasn't going to make any difference... I fired it up with the heater on high, and let it run for 20-25 minutes and then took it for a spin for another 20-25 minutes and I never heard the fans kick on, which was a great relief!! I did also notice that the fans were actually running, but at such a low speed that I couldn't hear them, so I assume that I had never heard them kick on medium/high speed before and they must have always been running as when they should have but I never noticed. I've included pictures of the old thermostat and coolant after I drained it. I'm amazed at how clean the inside of the radiator and thermostat housing are for a car that has 299,000 miles!!!