Hello everyone out there, I have came across an issue which I could use the help from more experienced users them myself. I have a 2003 Honda civic hybrid. I am experiencing overheating whenever I travel long distances but not locally. The coolant is getting pushed out the reservoir all over the engine compartment. So far I replaced the thermostat, the rad cap , and did a coolant flush and burped the air out and still overheats whenever I take it on a long distance. I checked the fans by puting on the ac and both fans came on. I was able to check the car while it was overheating and noticed that the fans came on but only for a short period of time. also the car blows cold air most of the time but warms up once I rev the engine past 3000 rpms. Not sure what It could be I did a block test on the car, and all three times the liquid stayed blue so I am not sure what It can be . After some research I was thinking maybe It is because I did not use a oem thermostat or rad cap, I used the failsafe autozone product. I was reading how sometimes there are minor differences between aftermarket and oem which effects the performance. I would like to avoid putting unnecessary parts into my car by switching to oem if that is not the reason why it is still overheating so any advice or tips on what to do would be highly appreciated. Also should I look into replacing the coolant fluid sensor that controls the fans ? and would the fans not working cause the overfill tank to overflow ?
I replaced the lower coolant sensor but replaced it with a autozone sensor is this something I should look at replacing ? The car is currently not throwing off any codes and doesn't overheat locally. I also tried to follow the service manual to fill and bleed the system but found that hard to do because when I would start the engine with the cap off it will go from low to start rising and overflowing , also when I try to bleed the air from the bleeder it takes a long time to have coolant coming out. The manual also said wait till the fans kick on (the thermostats opens ) but my fans do not kick on at all on idle only occasionally when overheating. Once again I thank you for the advice, The last thing I want to do is just throw parts at the car in hopes to fix it, this is my first hybrid

 

These are symptoms of a car with a bad head gasket/warped cylinder head. A very common issue with this generation of Civics - I just replaced the head gasket on my Civic that was doing exactly this. I've heard this is usually caused by not bleeding the cooling system properly - having air bubbles get trapped - causing hot spots - then causing damage that leads to a leak.

But in more detail,
I don't think your thermostat is the problem.
If the radiator hose by the thermostat is getting hot while the car is running (coolant is flowing) then I would say your thermostat is working properly. I would also expect the car to overheat no matter the driving conditions if the thermostat was not functioning and not opening and allowing coolant to flow through the radiator.
Your fans sound fine along with your temp switch. I can leave my civic idling for 10 minutes or so before the fans turn on the first time, then they shut off pretty quickly.

An intermittently working heater is a sign of air in the cooling system. Air can prevent the heater from working because it will block coolant from flowing through the heater core. Another symptom is hearing a gurgling/water bubbling sound from behind the dashboard from inside the car.
I take it when you say you did a block test and the fluid stayed blue - you mean you tested the coolant for presence of hydrocarbons (oil/fuel) and you expect the fluid to change a color if those are present. This is not what I would expect to hear, as you say "I would start the engine with the cap off it will go from low to start rising and overflowing" which to me, is a definite sign of a bad head gasket - especially if it does this far before the engine is up to temperature and could be boiling the coolant - air should not be bubbling through the coolant like that under any normal condition.

The way I diagnosed the head gasket on my car was that I had coolant leaking into the oil - I did not test the cooling system for contamination. If you have coolant in your oil, it will appear as a milky mixture on either your oil dipstick, or the inside of the oil filler cap with the same milky color. If you see sign of that - it's certain that you will need to have the head gasket replaced along with ensuring the cylinder head is true and flat.

My oil dipstick looked similar to the one pictured - the pictured oil cap is an extreme example of a pretty bad leak - or one that has been leaking for a long time.

- Good luck