Your Chevy S10 truck's water pump is responsible for sending the coolant into the engine. If you don't replace a bad water pump, the truck's engine will eventually overheat. Changing the water pump in an S10 can be relatively simple compared to other smaller vehicles that have more components in the way. The process can vary, however, depending on the truck's year and engine type, so it's a good idea to talk with your mechanic.
M/F Disconnect the truck's negative battery cable.
M/F Open the radiator cap in the engine, then open the drain plug on the radiator and let the engine coolant drain into a large container.
M/F Loosen the hose clamps for the upper air intake duct with a screwdriver and detach the duct. Unscrew and remove the upper fan shroud, remove the nuts connecting the fan clutch assembly to the water pump using a wrench and remove the fan clutch.
M/F Rotate the drive belt tensioner with a socket wrench, thus relieving the belt tension, and remove the drive belt. Unbolt and remove the water pump pulley.
M/F Detach the heater hose and the radiator hose from the pump if they are present. This should be the case on an S10 with a V6 engine.
M/F Remove the water pump's bolts with your wrench and remove the pump. If the pump does not come off easily, tap it with a soft hammer to break it free from its gasket.
M/F Wipe the mating surface of the engine block clean using a rag soaked with acetone or lacquer thinner.
M/F Apply RTV sealant to the replacement pump's gasket on both sides and then install the gasket on the pump.
M/F Install the replacement pump on the engine and apply the bolts, tightening them by hand first and then using your wrench while making sure the gasket does not slip out of position. Connect the hoses to the pump if needed.
M/F Reinstall the water pump pulley and then the drive belt with the socket on the tensioner. Make sure the belt follows the same path along the pulleys as before. A diagram should be available on the radiator shroud.
M/F Install the fan clutch assembly and the radiator shroud with their mounting nuts and screws and then connect the upper air intake duct with its clamps.
M/F Refill the engine coolant at the radiator filler neck. Use a fresh 50/50 mix of antifreeze and water if the old coolant is dirty.