In town your car relies on the electric fan to draw air through the radiator to keep the engine cool. Once on the freeway air flowing through the radiator should be sufficient to keep the engine cool unless for some reason the radiator is restricted internally or the thermostat is nt fully opening. Some cars (VW, Jaguar BMW) have problems with the water pump impeller failing not a typical Honda issue. Another possibility is a partially blown head gasket which is a Honda Civic problem. The most accurate way to test for a blown head gasket on a gasoline engine is to test for the presence of carbon monoxide in the cooling system. Snap-On, Matco (part # CO 2000), and Napa sell a tool to check to carry out this test. Another link to a supplier of this tool is http://www.etoolcart.com/combustion-leak-detector-lis75500.aspx. Carbon Monoxide is only present if there is a blown head gasket or cracked cylinder head. http://www.arrowheadradiator.com/head_gasket_or_combustion_leak_test.htm I think the napa part number 700-1006. http://www.blockchek.com/instructions.htm . Signs of a blown head gasket are coolant loss (frequently have to top up the coolant level of the engine without seeing an obvious leak), experiencing over heating or rough engine running or the presence of white sweet smelling steam from the exhaust. A badly blown head gasket may allow engine coolant and oil to mix.,
my car does not have a thermostat and once once on the freeway if i put it on nuetrual the temperture goes down fast and then i put on drive and i run a lil bit and it goes back i flushed my raidiater but that doesnt seem to be helping
Sound like a plugged exhaust system; Get your exhaust system checked from the engine to tail pipe. Check you’re self by carefully touching the exhaust system from tail pipe to engine. Should go from warm too hot where the exhaust system is restricted.