How to Change the Thermostat in a 2003 Chevy Malibu

The thermostat in the 2003 Chevy Malibu uses a spring to compress as the engine temperature increases. With the spring compression, more fluid flows through the engine and back into the Malibu’s radiator. The passage of fluid through the radiator lowers the operating temperature of the Malibu. This is how the vehicle regulates its own temperature and prevents engine overheating.

Follow the radiator hose from the radiator to the location where it mounts to the engine. The hose mounts to the engine by clamping to the thermostat housing.

Remove the clamp that secures the hose to the housing. Radiator hose clamps require a specialized tool for removal. If you do not have one, use a pair of pliers to squeeze the two tabs on the clamp together. With the tabs squeezed together, pull the hose off the thermostat housing. Some fluid may drain onto the engine block. Wipe up the fluid with a shop towel.

Remove the two bolts that hold the thermostat housing onto the Malibu with a 9/16-inch socket and ratchet. Lift the thermostat housing off the vehicle to expose the thermostat.

Pull the old thermostat out of the engine with your fingers and plug the hole with a shop towel. This prevents getting anything into the hole while you clean the engine.

Scrape the old thermostat gasket off the engine block and the bottom of the thermostat housing with a scraper and wire brush. Clean the mating surfaces with a shop towel.

Pull the towel out of the engine block and place the new thermostat into the hole. The end with the large spring sits inside of the engine. The jiggle valve sits inside of the thermostat housing.

Place the new thermostat gasket onto the base of the engine and place the thermostat housing on top of the gasket. Secure both with the 9/16-inc bolts.

Slide the radiator hose onto the thermostat gasket and secure it with the clamp.