History
My EP3 now has 105K miles on the odometer. I bought it approximately two years ago with about 80k miles. It is completely stock. It, like every single other Civic I have ever owned, overheats when sitting still in our (Texas) 110 degree summers for long periods of time, and I can't abide that/ would like to nip this problem in the bud.

I would say that I have an above-average understanding of cooling systems but I really wanted to get some feedback before I started chasing my tail or throwing a bunch of new parts at an unknown problem. I admittedly have a bad habit of being able to look at the problems of others objectively, but I view my own problems through rose colored glasses, and will often talk myself into thinking that I know the solution when I don't; a luxury that I only burden myself with. Haha.

Problem
The car overheats when it sits still. Thus far, the car has not overheated to the extent that coolant is spraying out or anything to that effect. It has only ever made it as high as 3/4 and I have experienced this approximately a dozen times in the past year. The problem rears its ugly head when I am sitting at idle for more than 15 minutes in the winter or in as little as 3-5 minutes when idling or moving slowly in the summer. So long as I can keep the car moving forward I can stave off the overheating, but in the lack of sufficient airflow, it wants to overheat quickly.

Variables, Both Known and Unknown
I believe that the radiator is without leaks. I believe that the hoses are without leaks. I also believe that the radiator fan is turning on; it just appears to be ineffective against the sweltering heat. I have not officially testing any of these variables, but I suspect that I am right and that the fan switch, hoses, et al are working correctly.

It has been suggested to me that the head gasket may be blown. I intuitively feel that this is wrong, but I am open to suggestion. I feel this is wrong because the car works fine, even when driven hard, so long as there is sufficient airflow and if the outdoor temperature is low enough. Having owned a car that did have a blown head gasket, I can say that it was obvious that such a problem existed irrespective of how cold it was outdoors. I really feel that this is an issue of a wimpy cooling system being put through the paces and losing out against mother nature when she's at her worst of 110 degree summers and bumper to bumper traffic. That being said, I'll listen to any suggestions.

What do you guys recommend? If worse comes to worse, I will go buy a racing radiator, some uber fans, a new fan switch, etc. and I will just completely overhaul the cooling system, erring on the side of overkill. This will be quite costly but if it works it will buy me piece of mind.

I would much rather fix the problem the right way, but it can get very costly taking the wrong approach to finally fixing the right problem. Thus, I would really appreciate any feedback so that I can get started on the right foot.

Thank you all in advance.

 

Sounds like a pretty severe overheating condition.

I was sitting in hours of traffic the other day in 97-100deg heat, although air intake temps were around 160deg, the coolant temps never exceeded 206deg. 101k mile car, original coolant (changing it this weekend).
From what I've read, the k series can be a pain to properly coolant flush without any air bubbles. Maybe go to honda and have them change/flush the coolant, perhaps they have a pressure test etc they can perform?

Assuming the fans, thermostat etc are working correctly, I'm thinking the previous owner changed the coolant improperly (air bubbles remaining), or used the wrong coolant?

 

First of all, you should definitely check and make sure that your fan is indeed turning on. If it is turning on and you've checked all your fuses (just in case) and you're sure there are no leaks, I would recommend flushing your cooling system and getting a new thermostat and coolant temperature sensor. I had a similar problem on my old EM2 and doing that fixed it right away. Also, make sure you use OEM Honda coolant from the dealer, all newer Honda's have a very sensitive cooling system. They're about $11 each and you'll need 2 bottles to flush your system. Here's a link to the temp sensor:
http://www.kseriesparts.com/cr/HON-37870-PNA-003.html
Rockauto or amazon might have it for cheaper

 

fans if you only overheat while not moving or moving slow your fans arent working good enough to flow air through the radiator.

 

Jump the fan switch and see if it turns on. Stick a paperclip in the two prongs of the plug. If it turns on, your switch is bad. Otherwise your thermostat may be busted.

 

Replace the cheap stuff first: Cap, thermostat, flush system, see how that works before you spend big bucks and overhaul it.