I have a 1994 Honda Civic Sedan that begins overheating if I drive it on the freeway for more than 10-15min. I can regulate the overheating for around 2 hours by turning on the heat, even at a low or medium setting. Obviously this is not the best solution. We replaced the water pump and thermostat about a year and a half ago for other reasons. I don’t think the engine fan is functioning; is there an easy way to fix it myself? Or is it probable that the overheating is caused by something else?
The engine fan isn’t needed on the freeway, and if it was the problem, it’d be a BIG problem around town. If it’s not overheating around town, then I’d guess it’s a partially plugged up radiator, you can get a replacement at Autozone, etc.
When driving at freeway speeds the radiator fan doesn’t function. That’s because there’s more than enough air being rammed thru the radiator to remove the heat. But if the radiator is partially restricted where not enough coolant is able to pass thru when operating at these higher speeds, the engine will start to overheat.
With the age of your vehicle, it’s not uncommon that it’s time for a new radiator.
I would check coolant level in the reservoir and the radiator, also pressure in the system. When the engine is cool take off the radiator cap it should have fluid to the top, replace radiator cap. At that point give the upper radiator hose a squeeze to feel what it is like with no pressure. If your coolant container has fluid at the recommended line, and the radiator is full, when warmed up squeeze the upper radiator hose. If it feels pretty much the same as when you checked it cool, your system is not holding pressure and that will decrease ability to cool also. You may be able to hear the cooling fan kicking in and out but if it is working. When warm with the heat off see if the fan blade starts spinning and correlate that to engine temp if you could.
Other possibilities include a bad water pump or a obstructed coolant flow, maybe a bad hose, maybe even a hose that looks good on the outside but is collapsed internally.
All suggestions here are good, but don’t overlook the possibility that the fins of the radiator could be full of bugs, grass, pet hair, etc. If so, the repair will cost nothing. In a dark garage, put a flashlight in behind the radiator and look at it as best you can through the front grill. The light should come easily through the radiator and A/C condenser. If it looks like it may be dirty, spray a garden hose through the radiator from the engine side. Stubborn cases require you to pull out the radiator to clean it so you can hose the radiator and condenser separately.