How to Change the Thermostat in a 1998 Chevy Astro Van

The 1998 Chevy Astro minivan is powered by the 4.3-liter Vortec engine with an automatic transmission. The thermostat housing is located next to the throttle body, on the intake manifold. The thermostat regulates when coolant cycles through the coolant system. The most common signs of a faulty thermostat are no heat in the passenger compartment or an overheating engine. Replacement of the thermostat will require draining some coolant. The 1998 Astro requires the use of Dex-Cool coolant, which cannot be interchanged or mixed with any other coolant.

Instructions

Removal

1

Park the vehicle on a level surface and set the parking brake. Lift the vehicle hood and support it with the hood prop rod. Let the engine cool completely.

2

Turn the radiator cap counterclockwise 1/4 turn and wait for the hissing noise to subside. Remove the radiator cap and set it aside.

3

Lift the front of the van into the air with the floor jack. Place the jack stands under the front frame rails, and lower the floor jack until the van rests securely on the jack stands.

4

Place the drain pan under the right side of the radiator, directly under the radiator drain cock. Rotate the drain cock counterclockwise until coolant begins to pour from the radiator drain. Allow about one gallon of coolant to drain and close the drain cock. Remove the drain pan from under the vehicle and store it in a safe place.

5

Loosen the clamp for the air intake tube at the air cleaner box, with a screwdriver. Remove the bolts securing the intake tube to the throttle body, with the socket and ratchet. Disconnect the wiring harness for the intake air temperature sensor. Remove the air intake tube from the vehicle.

6

Remove the nut securing the ground wire to the thermostat housing, with the socket and ratchet. Remove the ground wire. Remove the stud and the bolt securing the thermostat housing to the intake manifold. Lift the thermostat housing off the intake manifold and set it aside. Remove the thermostat from the engine.

7

Clean the mating surface on the thermostat housing and the intake manifold with the wire brush.

Installation

8

Ensure the new thermostat has the rubber gasket installed around its edge. Place the thermostat into the intake manifold.

9

Set the thermostat housing onto the intake manifold. Install the thermostat housing mounting bolt and stud. Tighten to 18 foot-pounds with the torque wrench. Place the ground wire on the stud and tighten the mounting nut with the socket and ratchet.

10

Set the air intake tube onto the throttle body. Install the securing bolts and tighten them with the socket and ratchet. Install the air intake tube to the air cleaner box. Tighten the securing clamp with the screwdriver.

11

Lift the van off the jack stands with the floor jack. Remove the jack stands. Lower the van to the ground.

12

Add fresh 50-50 Dex-Cool to the radiator until full. Start the engine and set the heater controls to the maximum setting. Allow the engine to reach operating temperature. As the engine warms up, the coolant level in the radiator may drop a little. Increase the engine speed to 3,000 rpm and hold it for three minutes to allow any air in the system to work its way to the top of the radiator.

13

Shut the engine off and top of the coolant level in the radiator. Install the radiator cap. Pour the drained coolant into the empty Dex-Cool container and take it to a local shop to have it recycled.