MandysAzul

Hi, I have an 05 civic dx that is having some odd overheating issues. Some backstory here, 4 months ago when I moved from the Bay Area to LA with my wife, we drove through some extreme central CA heat, nearly 7 hours of 115+ temps. Towards the end of the trip, her civic started to overheat right before we hit the mountain, so we left it there and came back for it the next day. The car would overheat while idling, but if I turn on the A/C, it forces on both fans and the temp holds, and I used that to get it home. So I knew the radiator fan wasn't coming on as it should, so I checked all the relays and fuses by jumping the terminals and found everything to be in working order, so I replaced the thermostat and coolant temp sensor, "bled" it (I can't believe there's no bleed screw, which is weird to me, but whatever) and the car ran just fine since then for over 10,000 miles.

Tonight, she was on her way home from work and suddenly the temp climbed up in the red, so she turned on the A/C again and it went back to normal. She used that to get home in light traffic, and a half mile from the house after hitting some stoplights, the car began to overheat even with both fans running, so she shut off the A/C and turned the heat all the way up, which got the car the rest of the way. So obviously the fans weren't coming on as they should have been, it took the A/C being on to run the radiator fan. So its the fan problem again, apparently.

Now I'm gonna fix it this weekend but I'm not sure what to think. The symptoms are the exact same as the last time, which would lead me to believe its the same part, but something has to be causing these coolant temp sensors to go out. It's a Duralast part from Autozone, and my experience is it is hit or miss with cheaper aftermarket stuff, so maybe I have myself to blame?

I made this post to see if anyone has had this exact same problem or can shed some new light or ideas on this one outside of the usual checking the relays and fans, coolant temp sensor and thermostat- I want to fix it once and fix it right because she needs to be able to safely rely on her car. I'd love to get some input and hopefully some ideas or experiences I haven't considered.

btw the head gasket is certainly intact; it was tested as a precaution after the last time I did this job, and there is no overflow coming from the coolant reservoir nor any bubbles in the radiator fluid.

Thank you all very much!!!

Slumpertcivic

First suspect would be the thermostat in my opinion.

As you said, the extra cooling effect of the second fan should have been enough to keep it in range, but if the coolant was not freely flowing towards the radiator..

ezone

Warranty the fan temp switch?
You said the reservoir isn't filling nor is it bubbling.....but is the radiator low?