How to Replace a Thermostat on a GM 4.0L SFI DOHC Engine

Iskandar Blogger 7:20 PM
How to Replace a Thermostat on a GM 4.0L SFI DOHC Engine

Dual overhead cam-driven engines have increased horsepower. This increased horsepower causes more stress on the engine. As the engine gets older, it stops cooling itself properly. When this happens, due to the increased horsepower you risk engine failure due to overheating. If your vehicle is equipped with a GM 4.0L SFI DOHC engine and you notice it is not cooling off properly, change the thermostat to prevent engine damage.

Instructions

    1

    Place the front end of the vehicle on ramps or jack stands. Secure the vehicle with the emergency break.

    2

    Drain the radiator fluid into a large drain pan using the petcock. Do not pull the lower radiator hose off to drain it. The petcock ensures a steady flow to ensure all the fluid makes it into the pan. With the fluid drained, close the petcock. If you cannot turn the petcock with your fingers, open it with pliers.

    3

    Follow the lower radiator hose until it dead ends on the engine block. The hose connects to the thermostat cover. Remove the clamp that secures the hose to the metal cover and pull the hose off the cover. The clamp is a compression clamp with two tabs on each side. Use a pair of pliers to squeeze the tabs together. This loosens the pressure the clamp has on the hose.

    4

    Remove the two bolts that secure the cover to the engine block with a ratchet and socket. Pull the cover off the engine. The O-ring, gasket and thermostat fall out when you remove the cover, so use caution when removing it.

    5

    Discard the old thermostat, thermostat gasket and O-ring. The O-ring is inside a groove on the bottom of the thermostat cover.

    6

    Place a new O-ring inside the groove on the bottom of the cover. Place a new thermostat inside of the thermostat cover. The end with the pin goes inside the cover. Place a new thermostat gasket on the bottom of the cover.

    7

    Place the thermostat housing, loaded with the thermostat, gasket and O-ring against the engine block with the bolt holes lined up. Secure the cover to the block with the original bolts using the ratchet and socket.

    8

    Place the hose back onto the metal cover. Squeeze the tabs on the radiator hose clamp with the pliers and slide the clamp back into place. Let go of the tabs to apply pressure on the hose.

    9

    Drain the radiator fluid back into the radiator using a funnel. If you use new fluid, use a 50/50 mix of radiator fluid and distilled water.