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Cooling fans working but temp gauge still goes up periodically then back to normal

My 1994 honda accord station wagons cooling fan is working but the temp gauge still goes all the way up then back to normal numerous times while driving… I park on the side of the road while the car is on, pop the hood to check and see any signs of over heating but the motor seems to be normal… What could be happening??

sounds like the thermostat opening and closing.

do you mean the temp goes up to the red zone?

It sounds like you have a thermostat that is failing. I would replace it before your engine really overheats.

Has the cooling system been serviced lately? It could be air in the system or a bad thermostat.

I had something similar happen on my 1998 Civic. It needed a new cooling fan and a new thermostat, but the temperature gauge barely moved.

My theory is that Honda designed our engines to run cool, making light use of the cooling systems. When your cooling system is working, the needle on the temp gauge shouldn’t move at all after the engine warms up.

I recommend you take your car in to a shop and have the cooling system tested. Get it fixed before you end up needing a new head gasket or a new engine.

This is why I change the thermostat every other coolant change.
Use only a Honda thermostat, not aftermarket.
Change the radiator cap too.

I generally agree with getting the OEM thermostat and radiator cap, but if you make sure the radiator cap has the right pressure rating, and you change it with every coolant change, you can go with an aftermarket one. In fact, the last aftermarket radiator cap I bought has a warning printed on it that it should be replaced with ever coolant change.

I have similar advice for the thermostat. You can’t go wrong getting an OEM thermostat, but if the aftermarket one you get has the following two features, it should be fine:

  1. Make sure it has the correct temperature rating.

  2. Make sure it is the new kind of thermostat that fails in the open position instead of the closed position.

If your thermostat has those features, and you change it with every other coolant change, you can get away with an aftermarket unit.

Air in the system is the first and simplest thing to check. Some Hondas have an air bleed screw near the thermostat housing but I have not found it on my 99 Civic. When I change coolant I have done this to get air out:

  1. Set the heater control to Hot. You’ll see the water valve on the firewall move as you move the heater from Cool to Hot. You want Hot so the heater core is open to the rest of the cooling system.

2, Elevate the front of the car on ramps or with jack stands. Take radiator cap off; fill to the top and start the car and idle long enough to get it up to normal temp. Place a pan to catch any coolant that spills - it is poisonous and should be put in a closed container ASAP. Never leave it open for an animal or person to sip. As air is expelled you may need to top up the radiator. Turn off the car, put on the cap. Fill overflow tank to correct level. Check the levels after the car has cooled after your next drive.

Does the temp go up while you are in slow traffic or a drive through? Notice the conditions it may be low pressure due to a bad radiator cap or something.

While you look around, check the radiator from the back side. Look for missing fins. They’re between all the tubes. If some are rotted away, you may need a new radiator too. If the radiator has any green or white coloring near the bottom, have a more thorough inspection done. With a really bad radiator, you will get red zone temps whenever you go up a long hill.

Check the coolant level in the radiator when the engine is cold. It should be full to the brim…If it is, I would replace the thermostat…