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The 4.3-liter engine was used in many Chevrolet vehicles, including the 2002 Chevrolet Blazer. This engine uses a timing chain, rather than a timing belt, and the bottom of the cover has a seal where the crankshaft snout passes through it. If the seal dries out or otherwise becomes damaged, oil leaks out of the seal. If you notice oil leaking, change the seal immediately, as a lot of oil is splashed in that area. Sooner than later, the engine will get too low on oil and the result will be extensive engine damage.
Step 1
Remove the negative battery cable, using the appropriate wrench, then set it aside, ensuring that it does not touch metal. Slide the drain pan under the radiator petcock. Loosen the petcock and allow the coolant to drain. Open the radiator cap so the coolant will drain faster. Dispose of the coolant in an appropriate manner, unless it is less than two years old and clean, in which case, you can reuse it.
Step 2
Loosen the radiator shroud and push it back over the fan, if it is a one-piece shroud. Loosen the fan pulley bolts, but do not remove them. Rotate the tensioner pulley toward the center of the engine, using the appropriate socket, to loosen tension on the belt. Lift the belt off the pulleys. Remove the fan pulley bolts and shroud as an assembly. If the fan shroud is a two-piece shroud, remove the top portion of the shroud, then remove the fan.
Step 3
Remove the crankshaft pulley, using the appropriate socket. Install the harmonic balancer puller onto the harmonic balancer, then turn the center screw clockwise to remove the balancer. Do not attempt to remove the balancer without the puller, as you will pull the weight ring off the rubber ring and destroy the balancer.
Step 4
Loosen the hose clamps on the heater and bypass hoses on the water pump, then pull the hoses off the pump. Remove the water pump using the appropriate sockets. Clean the gasket-mating surfaces of the water pump and block, using the scraper and rags.
Step 5
Jack up the vehicle, using the floor jack. Support the vehicle with jack stands. Slide a clean drain pan under the oil pan. Remove the oil pan drain bolt and allow the oil to drain. Dispose of the oil in an appropriate manner.
Step 6
Loosen the oil pan bolts, using the appropriate socket. Do not take all the bolts out. Unplug the crankshaft position sensor. Remove the sensor using the appropriate socket.
Step 7
Remove the front cover bolts, using the appropriate socket, then remove the front cover from the engine. Pry the seal out of the front cover using a small screwdriver or other pry tool, taking care to not distort the cover.
Step 8
Clean the gasket-mating surfaces of the engine cover, taking care not to score the cover, if you are reusing it. Smear a thin layer of RTV silicone on the cover, then position the gasket on the cover. Allow it to set for two to three minutes. Install the cover and tighten the bolts to 106 inch-pounds of torque.
Step 9
Coat the lips of the seal lightly with clean engine oil. Position the seal with the open end facing toward the engine. Install the seal into the cover, using the seal installer. Reinstall the crankshaft position sensor and plug it in. Tighten the oil pan bolts firmly.
Step 10
Lower the vehicle off the jack stands, using the floor jack. Reinstall the water pump (use a new gasket). Reinstall the harmonic balancer, using the balancer puller. Reinstall the crankshaft pulley. Reattach the negative battery cable.
Close the radiator petcock. Fill the radiator with coolant -- see the owners manual for the ratio of coolant to water. Start the vehicle and allow it to come to operating temperature. When the thermostat opens, top off the radiator with coolant. Reinstall the radiator cap. At the same time, check for oil leaks around the timing cover and oil pan.
Items you will need
- Set of wrenches
- Drain pan
- Set of sockets
- Harmonic balancer puller
- Scraper
- Shop rags
- Floor jack
- Jack stands
- Small screwdriver
- RTV silicone
- Seal installer
- Torque wrench (inch-pounds)
