05 Civic EX Temp Gauge malfunctioning

#1
This is my first post here, so if it is in the wrong place, let me know and I'll repost where it should go.

So here's the basic story.

05 Honda Civic EX.

About a month ago I'm sitting at a redlight and happen to glance down and notice my temp gauge working its way to H rather quickly. I plan to pull over but as soon as I start driving again it goes immediately back down. I'm a mile from home so I get home and check the engine. Oil isn't cloudy, no smoke, no check engine light, both rad hoses are hot...I begin to think I'm hallucinating.

The next day, it does it again. So I get some coolant, check the levels and they were low, so I top it off. It seems to run fine for a day or two.

Few days later, doing it again. So I think maybe my thermostat failed. Go pick up a new thermostat and gasket and replace it. I drive it around for a while and also let it sit and idle for about 15 mins. The gauge never get above about 1/3 of the way up (pretty normal for my car).

Few days later.....doing it again. So, I take it to the crappy pep boys. They do a coolant pressure test, say everything is fine. They then replace a temp sensor (think it was the one on the water bypass?? not sure). It runs fine for a day.

Day later, does it again. So I angrily take it back to pep boys and they bleed the lines and leave it running in the parking lot for about 2 hours and the temp never spikes.

Later that day, my temp gauge is still spiking while I'm sitting at red lights.

Now, it seems like the gauge is doing it just to piss me off. I check it when the gauge is sitting at H and the hoses are hot and there is no smoke and I have no idea what to do next.

Apologies that this is long, but I have no clue what else I should be testing. I'm not great with cars...I can change my oil and brakes and crap, but troubleshooting is not my forte. I think I've just been guessing.

If anyone has any advice, PLEASE offer it.
 
#2
I have the same exact problem now.. exactly.. mechanic idiots say it's ok..it's not.. my coolant bottle is full.. it was normal at the start of the day... Did you fix it? I think head gasket.. I'll junk it
 






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