1986 Honda Accord mileage: 262,000. I have recently noticed that the longer I drive the car the hotter it begins to run. It doesn't matter if sitting in traffic or moving. I can turn the heater on and it will come down a little, but never truly reaches normal operating temperature. Also, I notice that while the overflow reservoir generally has coolant in it, the radiator usually is down below the fins in the radiator and can take up to a pint of water to bring it back to the top of the filler neck. About three months ago it did have a small crack develop in the top around the filler neck that I was able to plug using that gas tank/radiator epoxy repair stuff and a tube of Prestone leak stop. My guess is that I do need to replace the radiator, just because it's old, but could this be a head gasket problem as well? Where is the water going to and why does it continue to work toward meltdown? Any suggestions?
Our first thought is that your problem may be the repair on the neck of the radiator you mentioned. For the cooling system to function properly, it must be airtight. As the engine cools between drives, a slight vacuum occurs in the radiator "pulling" coolant from the overflow tank back into the radiator. The vacuum may not be forming in your cooling system. Another possibility is a blown head gasket/cracked head. Have the radiator check for carbon monoxide (exhaust) being present in the system. This is a simple test with the proper equipment.