The General Motors V-6 engine in your Buick LeSabre presents some difficulties when you try to replace the serpentine belt. The front motor mount passing through the belt causes the problem. Removing and installing the belt requires you to first remove the front engine mount. Later models have addressed this problem by having a simple bracket that you can quickly remove to allow access to the belt.
Note how the old belt is routed. Making a drawing of the belt routing can make it easier to install the new belt, especially if the under hood routing guide sticker is missing. If the belt has broken, the belt routing can be found in a service manual (see Resource).
Remove the old belt by compressing the spring-loaded tensioner and slipping the belt off the alternator pulley. If your LeSabre has the engine package that does not require removal of the motor mount, the belt will simply pull out of the engine compartment, and you can install the new belt in reverse order. If you have to remove the motor mount, continue to the next step.
Position the floor jack under the engine with a block of wood between the oil pan and the jack. Then jack up the engine just enough to make good contact and support some of the weight. Remove the coolant overflow bottle. Remove the bolts attaching the motor mount to the frame, as well as the motor bracket. Then lift out the motor mount and remove the old belt.
Install the new belt, referring to the belt routing drawing or service manual, and slip it back onto the alternator while compressing the spring-loaded tensioner. Reinstall the motor mount and coolant overflow bottle, tightening the bolts securely. Start the engine, and check that the belt is routed properly and sitting evenly in the pulley grooves.
Remove the jack and the wood block before test-driving.
