Help Changing the Thermostat in a 1999 Chevy Malibu 6 Cylinder

In 1964, Chevrolet released the Chevelle, and "Malibu" was the name used for its top trim level. In 1978, Chevy replaced the Chevelle name with Malibu, and continued this model through the 1983 model year. In 1997, Chevrolet reintroduced the Malibu as a front-wheel-drive family car. The 1999 Malibu came standard with a 2.4-liter, four-cylinder engine and had an optional 3.1-liter V-6 available. A mixture of Dex-Cool coolant and water, regulated by a thermostat, kept the engine at an acceptable operating temperature. When the thermostat fails, the vehicle can either overheat or over-cool, depending on if the thermostat sticks open or closed. Replacing the thermostat in the V-6 Malibu requires removal of the air intake box and tubing.

Instructions

1

Raise the front of the Malibu, using a floor jack, and place jack stands under the vehicle's subframe. Lower the Chevy onto the jack stands.

2

Crawl under the Malibu and locate the radiator petcock on the lower, passenger's side of the radiator. Slide a drain pan under the petcock. Remove the drain plug on the side of the petcock, using a 1/4-inch drive ratchet, and turn the petcock counterclockwise to open it. Allow all of the coolant to drain from the radiator, close the petcock and reinstall the drain plug.

3

Raise the Malibu from the jack stands, using the floor jack, and remove the jack stands. Lower the car to the ground.

4

Locate the mass airflow sensor -- the metal tube connecting the air-filter box to the air intake tube. Disconnect the wiring harness from the MAF sensor by pressing the locking button and pulling the harness from the sensor.

5

Trace the air intake tube toward the engine and locate the intake air temperature sensor -- the only electrical sensor plugging into the air intake tube. Unplug the wiring harness plugging into the IAT sensor by pressing the locking button and pulling it from the IAT sensor.

6

Disconnect the breather tube -- the small, rubber tube plugging into the air intake tube -- by pulling it from the air intake tube. Loosen the hose clamps on either end of the air intake tube, using a Phillips screwdriver, and pull the hose from the throttle body and the MAF sensor.

7

Loosen the two nuts holding the air-filter box to the inner fender and pull the air-filter box and MAF sensor from the engine compartment.

8

Trace the upper radiator hose until you locate the thermostat housing -- the metal tube connecting the radiator hose to the engine. Pull the coolant surge tank hose -- the small rubber hose -- from the thermostat housing. Remove the thermostat housing-to-engine bolt and nut, and pull the housing from the engine.

9

Grab the thermostat and pull it from the engine.

10

Pull the rubber thermostat gasket from its seat in the thermostat housing. Scrape the thermostat housing-to-engine mating surfaces with a plastic gasket scraper.

11

Set a new thermostat gasket in the groove in the thermostat housing. Install a new thermostat into the engine with the spring side going into the engine. Installing the thermostat backwards will prevent it from functioning properly.

12

Reinstall the thermostat housing on the engine and tighten the bolt and nut to 18 foot-pounds, using a torque wrench and socket. Reconnect the coolant surge tank hose to the thermostat housing.

13

Place the air-filter box back in the engine compartment and tighten the retaining nuts to 3 to 4 foot-pounds.

14

Reinstall the air intake hose on the throttle body and MAF sensor tube. Tighten the two hose clamps. Plug the IAT sensor and MAF sensor wiring harnesses into their respective sensors.

15

Open the radiator cap and fill the radiator to the bottom of the filler neck with 50-50 premixed Dex-Cool coolant.

16

Start the engine and allow it to idle until the upper radiator hose becomes hot; this means the thermostat has opened. Add 50-50 premixed Dex-Cool until the radiator until the coolant level reaches the bottom of the filler neck. The entire cooling system on the 1999 Malibu holds up to 3.4 gallons of 50-50 premixed Dex-Cool.

17

Reinstall and tighten the radiator cap.