98civic missing coolant
 

this pertains to a 1998 Honda Civic LX, a/t, a/c, 230,000 miles

Over the last 6 or 7 months i find that every 3 or 4 weeks i have to add 1 or 2 cups of coolant to the overflow container in order to bring it up to the MAX level. Several thorough visual inspections of the engine and of the engine compartment have failed to locate any leaks, and there are never any puddles or even drips of the stuff on my garage floor. Where can the coolant be disappearing to? Could it be leaking head gasket? and if so, are there any specific tests i can perform to confirm that diagnosis, rather than just replace the gasket and hope that that will fix the problem? What else might account for the missing coolant? (The engine on this car never runs hot.)
Thanks in advance

coolant can be leaking into your combustion chamber and burning up with the fuel and air, it could be leaking into the transmission line if the the trans fluid is increasing in amount or turning colors it could be leaking into your oil if the oil is changing in color and increasing in quantity. You can check by doing a radiator pressure check and will have to do a visual into your combustion chamber with a boroscope. check your spark plugs, if you have a light carbon/black/ it is good, if too clean, water in the cylinder. I would not do a rad pressure check, this can blow out the weak head gasket and really cause a problem. With the amount of miles you have, more likley going into thru the headgasket. Check in the morning when cool if you have more steam out of the exhaust pipe then normal. After warm up, no steam should show.

this is a test i did on my civic when it had a bad head gasket get something clear that you can visibly see through and that will hold about 6 quarts of oil. drain all the oil into the clear container and let it settle for about an hour or so. since oil and water do not mix shine i light in different locations and look for seperation it wont be much seeing as how you are not loosing a lot but there should still be a little.