1993 Civic Runs Hot on Highway

Im having a problem where the car will start getting hot when on the highway at speed. The temperature gauge goes to . I can get it to cool down by turning on the heater with the fan on high. Idling or in stop
and go driving, the temperature gauge reads a little below half way. I replaced the thermostat and radiator cap. I do not seem to be loosing any anti-freeze. I bled the air out of the cooling system. The radiator fan seems to be working correctly as it goes on when the temperature rises. Im thinking that it might be the head gasket as these are known to be problems in the Civics, but I do not see any white smoke in the exhaust or water in the oil (no milky appearance). I would have thought that the problem would be more pronounced in stop and go driving due to less air flow past the radiator. Also, has anybody used the liquid head gasket sealers and did they work ? Any help would be appreciated.
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I had the same problem in my 1993 Honda civic, and if your driving with an orginal radiator, than I would strongly suggest replacing it. After I did this there was no problems with the car overheating. Remember, the radiator is over 12 years old and is made out of aluminum and will slowly get smashed, damaged, melted and well you get the idea.
I bought a new one off this guy: http://stores.ebay.com/ALL-NEW-PARTS-STORE
His prices are VERY reasonable compared to other ebayers, and he doesn't charge rip off prices on shipping. Some of these people who sell radiators ask like $50 but then another $70 for shipping, and that's a rip off.
I paid about $40+30 for shipping, and that's a great deal. Just email the guy if he doesn't have any listed, and make sure you buy a COPPER radiator, so you won't have anymore problems.
I had my copper radiator since march, and its been working perfectly. I had to drive around like you do, with the heat on and I live in Atlanta and it's daily 90+ and very humit. I know how much of a pain in the arse it is.
Good luck!
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Aluminum is going to keep your car running cooler but like mopa said, a copper one is going to be more durable, but heavier if weight is a concern. You could also try putting in a cooler thermostat. I have a 160* one instead of the stock which is 190* I beleive. Thermos are only like 5-10 bucks too.
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