I took out a loan and bought my 2004 Honda Civic LX with over 140000 miles on it from a dealership in Jackson Mo. After a couple months of driving it my car started overheating while driving back from Jonesboro. After making a stop I smelled something weird that I thought smelled like as I said to myself "it smells like someone around here is shooting fireworks or something" I didn't realize till looking down at my temperature while driving back the temperature gauge was all the way to the hot. I drove it all the way back even though your supposed to stop and let it cool down when it does this but I never stopped. I didn't know this at the time. Once I got back it was smoking like crazy under the hood. Absolutely no coolant in the radiator. Also caused the thermostat to go bad which also had to be fixed. I finally got the head gasket fixed and resurfaced for around a $1000. Really sucked!

As described by the other Civic owner the Rad level was low and the overflow to up too high. This was caused by exhaust gas being forced into the coolant at the head gasket. A combustion test of the coolant confirmed a very small leak. I got cold air of the heater when the coolant level fell too low and then put the overflow coolant back into the rad to correct . The condition was probably cause by a fan relay failing and the car overheating during a very long commute home one evening. We love the Si and got if fixed so we can drive it another 100,000 KM !

After my daughter noticed overheating (and stopped to let it cool down), I found coolant forced into the overflow and low coolant in radiator. This had to be 'corrected every 100-150 miles or it would overflow the overflow tank and the radiator would be very low. I switched cars with my daughter like a good dad should.

After just adding coolant, changing radiator caps and flushing the system didn't help, I found that I could remove the overflow and radiator caps and pressurize the overflow tank (small air compressor) slowly which pushed coolant back into the radiator. This saved messy overflowing and replacing coolant but was a nuisance.

I had the 200,000 mile timing belt/water pump change done at 187,000 and asked that they check the system but they found nothing. I finally concluded it was a head gasket creating a combustion leak/over-pressurizing the system. Rather than invest $3000 , I gambled with a $35 can of Bars Leaks Head Gasket Repair. It didn't seem to help at first but after a few weeks it got better and now I check the tank a couple times a month instead of every night. It's not perfect but I've gotten 13,000 miles out of it and still going. I might push my luck and try a second can.

Yes....the real answer is replace and machine but at 200,000 miles, something else is bound to make my decision for me.

Update from May 25, 2015: While I could maintain 'pushing' the coolant back into the radiator from the overflow tank forever, another daughter had need of a car. I went ahead and paid a local shop to do a cold compression check, which confirmed the need for a complete head gasket job, and then the usual routine including milling the head to make sure it is flat. Total pain, just under $1900. Ouch but maybe we will get lucky and go from 201,000 to 250,000 or 300,000.

Well I know this is a common issue on these civics. Luckily i caught it early without overheating the engine. Please keep an eye not only on your coolant reservoir but your rad as well. Here are my symptoms, so hopefully it can help someone diagnose their head gasket as well.

Symptoms: - Additional coolant in the overflow - Low coolant in radiator - Cold air out of heater (as a result of air in the system) - Pressurized radiator even after letting it sit overnight

Diagnosis: - Flushed coolant - Replaced thermostat - Replaced rad cap (I was hoping this was the reason) - Bled the system really well, however bubbles kept rising up out of the rad --> headgasket

The gasket was cracked in a couple places (very small and undetectable by a compression test), creating a combustion leak and over-pressurizing the system. Luckily the car never overheated - always keep an eye on your fluids and gauges. $2,300 is enough to pay... although I did get a tensioner and waterpump while I was in there. The job is not hard to do yourself, just takes time and patience.