How To Replace A Thermostat In A 1989 Honda Accord

Learning how to replace a thermostat in a 1989 Honda Accord is good knowledge to have, as the thermostat will eventually fail over time. If the thermostat sticks open or closed and causes the car to overheat or run too cold, it's time to replace it. Here is a breakdown of this fairly simple procedure.


  • Phillips screwdriver
  • Socket wrench and 13mm socket (and extension bar)
  • New thermostat
  • Honda coolant
  • Plastic container
  • Rag to clean up any spilled coolant
  1. Firstly, drain the radiator using the butterfly valve which is located on the engine bay side. Catch the coolant in a plastic container, you can reuse it but it is always good to replace it if it hasn't been changed for a while.
  2. Follow the lower radiator hose to the engine, you will notice a circular metallic shape which is the thermostat housing. Remove the hose by loosening the clip and collect anymore coolant which might drip out.
  3. Undo the four bolts holding the thermostat housing to the engine block. Access can be difficult and sometimes it is easier to remove the air filter and its piping as well as the associated wiring harness for the thermostat.
  4. Lift out the thermostat from the engine block and replace it with a new one. 
  5. Reattach the wiring, air filter and piping (if it was removed) and reconnect the lower radiator hose.
  6. Close the butterfly valve on the radiator and refill the radiator with the correct Honda coolant. Leave the radiator cap off and start the car.
  7. Let it run for twenty minutes to ensure that the fan kicks in at the correct time and that the thermostat is working. This procedure will also draw any air bubbles out of the cooling system. Refit the cap, close the hood and take the car for a twenty minute drive to ensure that the temperature gauge stays at a constant level.
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