The only sign or symptom that will appear signifying the belt needs to be changed is a seized engine. These are "interference" engines, which means if the timing belt breaks, pistons will start hitting valves, and other mayhem as the engine commits suicide, and invariably at the worst time and place. Replace the timing belt, water pump, and thermostat at the same time every 60,000 miles. If you have no record of when this was previously done, do it as soon as possible to prevent the aforementioned problems. It's not an inexpensive job, but much cheaper than a new motor. Enjoy your Lexus.
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