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Any sign of overheating, just replace the thermostat. On a 8 year old car it should be replaced and the cooling system serviced.
Check thermostat make sure fans work replace coolant easily done check manual
Replace it with the exact same temperature thermostat as the one you removed. Do not run the engine without a thermostat. The thermostat is required to keep the engine running at the optimum temperature that will give the best performance and mileage. If it is overheating running it without a thermostat is not the solution.
If it is overheating or taking a long time to reach full operating temperature then it may need a new thermostat. If you even suspect it is not functioning properly just replace it.
Check to make sure you have the correct mixture of anti-freeze and water because anti-freeze also helps with overheating too. If you still have a problem check your thermostat. It could be stuck closed and may not be opening.
Primarily an overheating condition, but before you jump to an expensive conclusion try replacing the thermostat first.
Stuck Thermostat, or defective cooling fan/thermal relay, would be my guess.
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Low coolant? Cooling fan not working? Thermostat not opening? Radiator restricted or plugged? Water pump not circulating coolant? System airbound?
A 1991 Honda Accord could be overheating if the radiator has a leak. There could also be a problem with the head gasket.