How to Replace the Thermostat on a 2004 Chevy Impala 3.8L

Written by marion cobretti
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How to Replace the Thermostat on a 2004 Chevy Impala 3.8L
(Jupiterimages/Comstock/Getty Images)

The thermostat in your Impala works similarly to the thermostat in your home by controlling the flow of coolant through the engine. As the engine heats up, the thermostat opens to allow fresh coolant that has already been cooled by the radiator fan into the engine. The hot coolant that once surrounded the engine automatically gets recirculated to the radiator for cooling. The process continues until you turn off the engine. You should replace the thermostat in the 3.8L 2004 Chevy Impala if you suspect that it's defective. You can do the repair right at home in 40 to 45 minutes with a few tools.

Skill level:
Moderately Easy

Things you need

  • Coolant drain pan
  • Socket wrench
  • Shop rag
  • Thermostat with gasket
  • Funnel

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  1. 1

    Raise and support the bonnet on your Chevy Impala. Remove the cap on the radiator by pushing down on it while turning it to the left.

  2. 2

    Locate the drain plug on your Impala's radiator. The plug attaches to the bottom-right corner of the radiator on the driver's side. It's recessed into the radiator and the top of it has a flat tab on it, about as long as the tip of your finger.

  3. 3

    Place a coolant drain pan under the drain plug of the Impala's radiator. Before you open the drain plug, keep in mind that you only have to drain half of the coolant, which should take about 80 seconds.

  4. 4

    Reach down into your Impala's engine compartment and begin turning the drain plug on the radiator counterclockwise by hand. As soon as you see coolant start to come out of the drain plug, begin counting to 80. Start closing the drain plug when you reach 77 seconds.

  5. 5

    Follow the large round, top radiator hose over to its connecting point on your Impala's engine. The rounded housing that the hose attaches to is the thermostat's housing cover.

  6. 6

    Remove the bolt on the left and right side of the housing cover with a socket wrench. Lift the housing with the hose still attached to it and move it to the left. Remove the thermostat by simply pulling it out by hand.

  7. 7

    Remove any remaining gasket debris from the housing cover and the thermostat's mounting location. Wipe both surfaces dry with a shop rag.

  8. 8

    Insert your Impala's new thermostat back into position on the engine. You should not be able to see the spring on the thermostat. If you do, the thermostat is upside down. Place the new gasket that came with your thermostat down over the new thermostat. Make sure the two holes in the gasket line up with the bolt holes used to secure the housing cover in place.

  9. 9

    Move the housing cover back over and lower it down onto the new thermostat. Thread the two bolts by hand. Tighten the two bolts with a 3/8-inch drive torque wrench set to 19ft.-lbs. until secure. Place a clean funnel into your Impala's radiator fill hole. Pour the coolant in the drain pan through the funnel back into the radiator. Put the radiator cap back on and push down on it while turning it to the right to secure it. Start the engine and check around the thermostat housing cover to make sure it's not leaking coolant.

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