i have a 2002 honda civic ex and i've been having overheating problems. it started out early this summer so my dad decided to start off with the little things:
- making sure the fan was working
- replacing thermostat

didn't fix the problem. i found myself loosing a lot of coolant as well. again, my car began to overheat. he then fixed:

- new radiator
- new radiator cap
- made sure the water pump was good
- couldn't find any leaks

usually , i can bring down the temperature of my overheating car by turning on the heater. ever since i got a new radiator, my car began to act up again. this time, the temperature would only get 3/4 of the way up as opposed to the little needle rising all the way to the top. it would also fluctuate. i noticed it would begin to get a little hotter than usual and would stay there while i was still driving (sometimes, other times it would go up). as soon as my car was idle, the temperature started to rise.(sometimes, other times it would go back down) i turned on the the heater and found it was blowing cold air-first time it did this (yesterday NIGHT to be exact).i then checked the coolant level in my car as well as in the resovier-full. today, i noticed there was a lot of leaking coolant on the passenger side of my car and when i opened the radiator cap to check to see if there was any coolant, it was pretty much empty. i drove it for about 30min max in town today when the temperature again began to flucuate. i do not know what it could be. here are my questions:
-im starting to think that maybe its the heater core. how can i KNOW if it's the heater core?
-and if not, what else can it possibly be?
- also , i seem to be confused, do i add coolant through the radiator cap OR in the little white bottle (resovier) on the side?

i need help. please and thanks!

 

well find the leak, and you can add it through either the little resovouir is to show how much is in there

 

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https://honda-tech.com/forums/honda-civic-2001-2005-78/2005-hond-civic-ex-overheating-2555660/
https://honda-tech.com/forums/honda-civic-2001-2005-78/01-civic-intermittent-overheating-2339016/
https://honda-tech.com/forums/honda-civic-2001-2005-78/2001-honda-civic-overheating-2519383/
https://honda-tech.com/forums/honda-civic-2001-2005-78/car-overheating-2231053/

There are many, many more.

If the coolant is filling the reservoir and then spilling on the ground, my guess is that your head gasket needs to be replaced.

 

Find where the leak is at...
once it start to overheat pull over and inspect for the leak...with engine still on if safe to do so

overflowing resovior = head gasket.. in my case of overheating.

check your hoses, waterpump for leaks

fill coolant thru radiator cap when coolant/engine is hott is unsafe...use towell to cover cap to protect from burn, fill thru resovior as a fluid top-up..in yur case use fill thru radiator as a quick fix to yur overheating problem as u can get more coolant into the system untill u get it fixed propperly.

 

same thing was happening to my 2001 ex. changed everything you did aswell and ended up being the headgasket. its such a minor seperation that the oil is still clean and probably cant be detected with the gas analyzer. just go for the headgasket and while your at it change the intake mani gasket. they come with some rubber thing that detiorates and should be replaced. since your in there do timing belt, water pump all the misc. seals.

 

possible head gasket as well did that on my 03 and then did some other work and it worked fine

 

Did anyone notice oil between the head and the block on the passenger side of the engine? I wonder if its a common place for the head gasket to leak. And so many people are having the same trouble with this generation of the civic... I wonder why Honda didn't do something about it.