Most of us welcome the opportunity to save significant money by tending to some basic and intermediate car care on our own. Replacing a thermostat can be challenging, but you can be successful if you plan properly and take your time with each step. If your car shows signs of overheating when stopped but cools down when in motion, it may be a sign that your thermostat needs to be replaced.
Drain the coolant from your radiator. Use a socket wrench to remove the drain plug from the bottom of your radiator, if necessary. You also have the option of disconnecting the lower radiator hose from the unit. Use the appropriate screwdriver to loosen the O-clamp and pull off the hose. Make sure to use a drain pan to catch all of the antifreeze as it drains from the radiator.
Remove the engine cover. On the Kia Sedona, it's the large, grey composite piece that sits right in the top centre of the motor. Use the appropriate screwdriver (such as a Phillips) to remove the six screws that hold the cover.
Take off the air intake. There are two Phillips head screws that hold the air intake in place. It's very quick to remove, and is located just to the right-centre of the motor.
Move the air filter box. There are three Phillips head screws that hold the air box in place. It is also quite easy to remove. At the rear of the air box is a skinny hose that you need to remove in order to pull the entire assembly from the engine compartment.
Remove the radiator hose by loosening the O-clamp that holds it on to the radiator. Removing the radiator hose gives you a little more hand room so that you aren't busting your knuckles on all of the engine parts.
Take off the thermostat housing. This has three bolts and takes a bit of patience and work to complete. Two of the bolts are tough to move. The easy one should be the one you'll see and is closest to your position. The second one requires you to gently push some wiring aside to fit your hand in place. The third one on the back side of the housing is the one you have to feel for and remove without seeing it. Keep in mind, you'll have to replace it in the same way.
Remove the malfunctioning thermostat. It won't be easy to do with your fingers, so I recommend you do this with a pair of needle nose pliers. The thermostat may be held in place because of vacuum, and the pliers give you the necessary leverage to twist it a bit to pull it loose.
Replace the old unit with your new thermostat and gasket. Once installation is complete, put all of the engine parts you've removed back in place by reversing the steps above. As with most do-it-yourself auto tasks, you will likely find that putting everything back the way it was is much faster than breaking it all down for the repair. Remember to fill your radiator with the proper level of coolant per the manufacturer's recommendations.
Perform this repair when the engine is cool to avoid getting burnt by hot coolant or engine parts. Consider replacing all of the screws you've removed with new, stainless steel ones as the original screws are very likely rusted by the time you have to replace a thermostat.
Make absolutely sure to use a drain pan to catch the draining coolant. Antifreeze is poisonous to humans and animals, and the sweet scent tends to attract thirsty animals. Clean up any spills.