I have a 93 Honda Civic LX. About six months ago I began noticing a small leak some where in the system because every few hundred miles it would need about a quart of coolant added. The fan comes on as it should and other wise the car runs great.
Last week though it overheated on me. I had some water in the trunk and I was able to nurse it home. The next day I let it run and tried to find where it was leaking from. Once the engine got hot it seemed to port all the coolant out of the over flow tank cap. The cap is on tight and so I took out the radiator and inspected it as well as all the hoses to se if I could find an alternate leak but no luck. Tried it again today and once again it ran fine for a couple miles then spewed out the over flow cap on the plastic tank. (as best I can tell) any sugestions? Is my radiator to clogged to function right?
No sign of water getting into the oil and the outflow and intake coolant hoses seem to be the same temp. I can't find anywhere around the radiator that appears to be wet except from the overflow tank leak.

 

First and most inexpensive part to check/replace is the radiator cap. Then the Thermostat. Those 2 items are the most common. Yes the radiator may still be the cause, but less common than the previous ones mentioned. Another possibility is the head gasket might have a small leak and the coolant that is entering the chamber is just going out of the exhaust as vapor/steam, therefore there would be no signs of coolant leaking.

 

So I have a new radiator cap and thermostat installed. Still overheating. Can't find a leak anywhere but where it blows out the overflow tank. The coolant seems to be very foamy. I think maybe its time to take it into the shop unless anyone has any more ideas. I don't think I have a leak in the system because if it was leaking out it wouldn't be pumping it out in to the overflow tank right? Seems to overheat after driving about 20 miles and then when I'm sitting in line at the Taco Bell drive up bam..... over heats.

 

Have you tried bleeding the air out of the system. There should be a small bolt near the thermostat housing. Connect a section of clear hose here and open the bolt. With the engine running watch the coolant coming out the hose for bubbles. Once the bubbles stop close the bleeder and make sure you don't allow the coolant to go too low when bleeding or you'll have to start over. I've found in the past that too much air in the system can cause these kinds of overheating problems as well. Best of luck and let us know if this helps.

 

possible head gasket? check your oil to make sure it isnt "foamy' like your overflow tank-----if it is ---head gasket time --but u should take it to the shop anyway get another opinion

 

if the coolants foamy, then its likely its a headgasket. its not foolproof, but a couple other checks that are simple to do are compression checks, and check to see if the oil is a milky white color. if so, then its headgasket, if not, then it still might be[&:] but thats not too big of a deal if you are mechanically inclined.

 

So I took it into the shop and they bled the air out of the system ran it for about a half an hour (I had all ready driven it for twenty minutes before that to get to the shop and it never would over heat. They said everything looked good. I went on home and as I pulled into the drive it overheated again. Do you think it might be a sensor. The temp always sits in the same place until it overheats and then it shoots up, pegs out and starts spraying out the cap of the over flow tank? What gives...........

 

Is their some sort of computer or sensor logic other than the thermostat that could be sticking and not alowing coolant to run back and forth to the radiator freely?

Could it be overheating simply because I am only running water in the radiator and not antifreeze?

Any other wild ideas I can't think of?