How to Replace the Thermostat on a Chevy Uplanderby Robert Moore; Updated November 07, 2017
Items you will need
3-gallon drain pan
3 gallons Dexcool pre-mixed 50-50 coolant
The thermostat on your Chevy Uplander is located on the lower, passenger-side corner of the engine. If you have the 3.5-liter engine, it is located just above the air conditioning compressor. If you have the 3.9-liter engine, it is almost in the same location, but directly above the oil filter housing. The process for either engine is the same. And in either case, you must properly fill and bleed the cooling system to complete the repair.
Park your Uplander on a level surface and set the parking brake. Lift the front end into the air. Position jack stands under the flats in the subframe rails -- located between the lower control arm mounts. Lower the front end onto the jack stands, and open the hood.
Wait for the engine to cool completely. On 2005-to-2007 models, loosen the radiator cap 1/4 turn. Once the pressure escapes, remove the radiator cap. On 2008 models, do the same for the coolant pressure cap on the passenger side of the engine.
Place a drain pan under the corner of the radiator on the driver side. Locate the drain cock and turn it counterclockwise. When the coolant is drained, close the drain cock, then remove the drain pan. For now, store this used coolant in a place not accessible to children or animals.
Find the thermostat housing on the lower, passenger side of the engine. Squeeze the clamp on the hose at the thermostat housing with locking pliers, then slide the clamp back on the hose. Twist the hose, then remove it from the thermostat housing.
Remove the nut from the thermostat housing stud, using a socket and ratchet. Remove the plastic harness retainer from the stud. Remove the housing stud and bolt, then remove the housing from the engine. Remove the thermostat, noting its orientation. Remove the thermostat gasket from the engine block.
Remove any remnants of gasket material from the mating surface of thermostat housing and the engine block with a soft wire brush. Make sure no gasket material remains on either surface.
Install a new thermostat with the spring pointing into the engine block. Place a new gasket onto the thermostat housing, then install the housing. Tighten the bolt and stud to 18 foot-pounds with a torque wrench. Press the wiring harness retainer onto the thermostat housing stud, followed by its nut.
Slide the lower radiator hose onto the thermostat housing. Slide the hose clamp into place, then release the locking pliers. Lower the front end of your Uplander.
Add fresh 50-50 premixed Dexcool coolant to the cooling system through the radiator fill neck, or the pressure cap opening if you have a 2008 Uplander. The coolant should hold steady at the base of the fill neck on either engine.
Install the radiator or coolant pressure cap. Tune your heater controls to maximum heat and defrost settings. Start the engine. Run the engine at 2,500 rpm until the engine reaches operating temperature. Let off the throttle and let the engine run at idle speed for at least three minutes. Shut off the engine and give it two hours to cool. Once it cools, top off the coolant system and repeat this step. You may have to repeat it several times before the coolant holds at the "full cold" level after the engine has cooled down.
Pour the coolant you drained into the empty coolant containers. Turn the used coolant into your local shop or parts store for recycling.
Engine coolant is poisonous to humans and animals -- always store it out of their reach. Do not attempt to release cooling system pressure on a hot engine. The sudden release in pressure may cause the coolant to flash boil, which can cause serious injury.