See Figures 1 through 9
Only the 2.3L B Series Pick-up and 3.0L MPV engines use a rubber timing belt. All other engines use a timing chain, and no periodic inspection is required.
The 2.3L B Series Pick-up and 3.0L MPV engines utilizes a timing belt to drive the camshaft from the crankshaft's turning motion and to maintain proper valve timing. Some manufacturer's schedule periodic timing belt replacement to assure optimum engine performance, to make sure the motorist is never stranded should the belt break (as the engine will stop instantly) and for some (manufacturer's with interference motors) to prevent the possibility of severe internal engine damage should the belt break.
Although these engines are not listed as interference motors (a motor whose valves might contact the pistons if the camshaft was rotated separately from the crankshaft) the first 2 reasons for periodic replacement still apply. Mazda does not publish a replacement interval for this motor, but most belt manufacturers recommend intervals anywhere from 45,000 miles (72,500 km) to 90,000 miles (145,000 km). You will have to decide for yourself if the peace of mind offered by a new belt is worth it on higher mileage engines.
But whether or not you decide to replace it, you would be wise to check it periodically to make sure it has not become damaged or worn. Generally speaking, a severely damaged belt will show as engine performance would drop dramatically, but a damaged belt (which could give out suddenly) may not give as much warning. In general, any time the engine timing cover(s) is(are) removed you should inspect the belt for premature parting, severe cracks or missing teeth. Also, an access plug is provided in the upper portion of the timing cover so that camshaft timing can be checked without cover removal. If timing is found to be off, cover removal and further belt inspection or replacement is necessary.