The 1998 through 1990 Buick LeSabre 3.8-liter engine uses a timing chain, rather than a timing belt. You should check the chain every 120,000 miles, but unlike a belt, it does not need to be changed unless it is rattling. In most cases, it warns you that it is going to malfunction because it rattles against the timing cover when it gets loose. If you hear that, replace the chain immediately.
Disconnect the negative battery cable using the appropriate wrench. Set it aside, ensuring that it does not touch metal. Slide the drain pan under the radiator petcock. Ensure that the engine is cold. Loosen the petcock and remove the radiator cap. Allow the coolant to drain. Discard the coolant in an appropriate manner because it is poisonous for small children and animals.
Rotate the accessory drive belt tensioner pulley toward the center of the engine using the appropriate socket, then lift the belt off the pulleys. Allow the tensioner to rotate back into place. Do not let it snap into place. Rotate the tensioner with your hand. If it does not rotate freely or grinds, replace it.
Disconnect the heater pipes using the appropriate line wrench. Loosen the hose clamps on the lower radiator hose and the bypass hoses using the screwdriver, then pull the hoses off the front cover.
Break the lug nuts loose using the lug wrench, but do not remove them. Jack up the front of the vehicle using the floor jack, and support it with the jack stands. Remove the front wheels using the lug wrench. Remove the inner splash shield using the appropriate sockets.
Remove the crankshaft balancer retaining bolt, then remove the balancer using the harmonic balancer remover. The balancer on this vehicle has smaller holes than most balancers, so you need a harmonic balancer removal tool specifically for the Buick LeSabre. Tag the electrical connectors on the camshaft sensor, crankshaft sensor and the oil pressure switch. Unplug the connectors.
Slide an empty drain pan under the oil pan. Remove the drain plug and allow the oil to drain out. Reinstall the drain plug. Slide the drain pan under the oil filter. Remove the filter using the oil filter wrench. Discard the oil and filter in an appropriate manner.
Remove the oil pan-to-front cover bolts, using the appropriate socket. Remove the front cover mounting bolts, using the appropriate socket; then remove the front cover. Pry the front cover oil seal, which is the round seal in the bottom center of the cover, out of the cover using a screwdriver. Remove the gasket. Clean the gasket-mounting surfaces with the plastic scraper and shop rags.
Remove the camshaft thrust button. Line up the timing marks on the sprockets until they are as close together as possible. Remove the spring and damper assembly from the center of the crankshaft using the appropriate socket. Remove the camshaft sprocket bolts, then remove the sprocket and timing chain as an assembly. Remove the crankshaft sprocket using the appropriate socket.
Clean the gasket-mounting surfaces on the engine with the scraper and rags. Clean the sprockets with the rags.
Position the timing chain the camshaft and crankshaft sprockets, making sure the marks line up on the two sprockets. Hold all three pieces together, then slide the assembly onto the camshaft and crankshaft. Install the camshaft sprocket bolts and tighten them to 27 foot-pounds of torque. Line up the camshaft sprocket mark with the balancer shaft mark.
Reinstall the thrust button and the spring and damper assembly. Tighten the bolt to 15 foot-pounds of torque. Reinstall the front cover assembly in reverse order of removal. Reinstall the negative battery cable. Tighten the petcock. Fill the radiator with 50/50 antifreeze. Install a new oil filter. Fill the engine with the appropriate type and amount of oil according to the information in the owner's manual. Start the vehicle and allow it to come to operating temperature. Check for leaks. When the coolant drops, the thermostat opens at normal operating temperature, so top it off.
