You should not have pressure in the radiator with the engine absolutely cold. That really suggests a leak in the engine. There is a test kit made to analyze the gas in the radiator and see if it is combustion product from a leaky head gasket, or just air.

 

I believe you may have air in the system. At least it is an easy thing to rule out. Get the front of the car on an incline, with the radiator cap at the highest point. Take off the radiator cap and fill with 50/50 water antifreeze. Start the car, turn the heater to full hot and wait for the thermostat to open. You can tell the thermostat has opened when the upper radiator hose and the lower hose are both at the same temperature. If the radiator gurgles/spits it has air in the system. Rev the engine and the air will blow out. You may have to do this a few times to evacuate all of the air bubbles. You should only see fluid circulating evenly and noislessly as you peer down the filler neck. If there are no gurgles/spits ever, and you can watch the flow increase smoothly with RPM's, as you would imagine your water pump spinning faster with engine speed, then everything is good. I think your thermostat failed originally, as evidenced by no heat when you turned on the heater, and then air was trapped during that replacement. When the bubble gets trapped in the thermostat housing there is insufficient thermal information to the thermostat itself to open. Just a guess, but worth 30-45 minutes of effort and a few ounces of antifreeze.

 

Ed,

I just tried this. The car took FOREVER to get to speed with the heat blasting. It was holding at about 1/4 (little higher) until I turned the heat off for a bit to get the temp up to operating.

Once at operating temperature it didn't look like the fluid was moving at all. The fans never kicked on either...which was odd. I started revving the engine with the throttle and every once in a while the fluid would swirl, raise, start to overflow and I would let off the throttle. Once I did that, it receded and then let out a bubble. If I didn't touch the throttle nothing would happen.

The entire time, once the car was up to operating temperature a faint white mist was coming from the radiator opening. This was almost unnoticable.

 

When the radiator released the gas bubble, did the coolant level drop substantially? If so, did you top off the radiator and reservoir with coolant after the procedure? Did the procedure eliminate the overheating problem?

 

The coolant level remained the same. I haven't driven it since the procedure, as I am literally scared to death of driving more than 5 miles from my house in the car.

I'm throwing my hands in the air, it's going to Honda tomorrow for a diagnosis.

 

Sounds like an issue with your thermostat, make sure you keep fluids in there until you get it fixed or you'll burn up your engine quick.

 

Post #27 in this thread listed parts already replaced. Among these was the thermostat.

 

i have a bmw as a DD and it overheaded when ideling....
it turned out to be the a/c condensor fan... not the cooling fan inside the engine... i don't know if civics have them since i am new but that fiixed my bmw... but change the coolant if not.. its good to change that crap anyways... replace the thermostat while ur there... it will be better for the car

 

HO-LY ****!

I am sooooooooooooooooooooooooooooooooooooooo screwed. Honda diagnosed the problem immediately. The car needs a new cylinder head (top of the engine). The block is fine. They also said that the radiator my mechanic put in wasn't honda approved (sounds like bs) and the thermostat went again (fried itself out).

They quoted me at $4,200 and then told me I shouldn't do it....lol

What do I do?

 

What finding by Honda led to the conclusion of a bad head/head gasket?