Inspect the belt for any visible signs of damage such as missing teeth, deep cracks or scores, or loose threads along the edges of the belt. Check that there is no oil or antifreeze leaking onto the belt, as this will soften the rubber compound and cause premature failure. As as average rule of thumb, the timing belt should be replaced every 60,000 miles (96,000 km). If the belt breaks while the engine is running, or the crankshaft and/or camshaft has been turned separately after the timing belt has been removed from the engine, the valves may strike the piston heads, and cause engine damage. If replacement is necessary, follow the precedures very closely.