Chevy's 2001 S-10 trucks equipped with the 4.3-liter engine used a thermostatic element to regulate engine temperature. The thermostat should start to open at 188 degrees F and be fully open at 206 degrees F. If the thermostat fails to open or opens slowly, your S-10 will overheat. Assuming the cooling system isn't losing pressure or fluid and the engine coolant temperature sensor isn't faulty, it's time to consider a look at that thermostat.
Items you will need
- Clean catch pan
- Rubber tubing
- Ratchet set
- Socket set
- Gasket scraper
- Shop rag
- New thermostat gasket
- Foot-pound torque wrench
- Inch-pound torque wrench
- Fresh pre-mixed 50-50 Dexcool coolant
Park the S-10 on level ground and wait for the engine to cool. Loosen the radiator cap 1/4 turn and wait for the hissing to dissipate. Remove the radiator cap.
Find the radiator draincock at the lower, driver-side corner of the radiator. Position a clean catch pan under the draincock and slide a small piece of rubber tubing onto the draincock's nipple. Lead the tubing into the catch pan. Open the draincock until about one gallon of coolant drains from the system and then close the draincock and remove the tubing.
Disconnect the breather tube from the air cleaner outlet duct. Unplug the intake air-temperature sensor harness from the intake duct electrical connector. Remove the outlet duct retaining wingnut. Loosen the hose clamp holding the duct on the mass air flow sensor and gently work the duct off the MAF sensor. Remove the outlet duct from the engine compartment.
Find the throttle cable standoff bracket on the throttle body. Remove two mounting nuts and move the bracket aside enough to gain access to the thermostat housing on the lower intake manifold. Remove the thermostat housing bolts. Lift the housing off the block and set it aside.
Remove the gasket from the sealing surfaces, using a gasket scraper if necessary. Remove the thermostat from the engine. Clean the sealing surfaces on the water outlet housing and the engine block with a shop rag. Ensure that the surfaces are clean and dry.
Install the new thermostat in the engine block with the spring pointing into the engine. Install a new gasket. Install the water outlet housing and torque the bolts to 14 foot-pounds, using a foot-pound torque wrench. Install the throttle cable standoff bracket on the throttle body. Torque the bracket nuts to 89 inch-pounds, using an inch-pound torque wrench.
Install the air cleaner duct on the MAF sensor. Torque the hose clamp to 35 inch-pounds. Plug the intake air-temperature sensor harness into the intake duct electrical connector. Install the outlet duct retainer wingnut and tighten it firmly. Reconnect the breather tube to the duct.
Inspect the drained coolant and replace it as necessary using approved coolant. Add coolant back to the radiator until the coolant level is 1/2 inch below the filler opening. Start the engine and allow it to warm up until the thermostat opens and coolant begins to flow through the radiator. Add coolant as needed until the level remains full to the top. Install the radiator cap. Check the level in the coolant recovery reservoir and add coolant as needed.
- Lubricate the intake duct with a soapy solution prior to installation if the duct is difficult to reinstall.
- Draining the radiator removes only 60 percent of the coolant in the system. To completely drain the cooling system, remove two hex-head drain plugs -- one on each side of the engine block -- towards the rear of the block near the rear freeze plugs. Allow the coolant to drain. Apply a sealer to the threads, reinstall the plugs and tighten them to 13 foot-pounds.
- Tempilsticks are available to test the thermostat's operation you've removed it from the engine; but honestly, if you went through the trouble to remove it and it hasn't been changed in a while, go ahead and install a new thermostat.
- While most trouble is caused when a thermostat fails to open, sometimes a thermostat will fail to close. If your thermostat fails to close, the engine is slow to reach operating temperature and air from the passenger compartment vents won't get very warm.
- Do not open the cooling system when it is hot or under pressure.
- Dispose of used engine coolant according to local regulations.
- Do not allow solvents or lubricants to contact the sensing elements inside the MAF sensor.
- GM Service and Parts Operation Manual, 2001 Chevrolet/Geo S10 Pickup - 2WD; General Motors Corporation