The condition of the timing belt without removing the plastic shroud or valve cover impossible to know. But even in this case, the outer side of the belt will show nothing. To determine what his degree of wear, inspect its inner side, to do this, turn it inside out. When checking the belt, pay attention to the commercials. Often they become a cause of breakage of even the highest quality belt. If the timing belt is worn, before replacing, inspect and, if necessary, adjust the rollers. Before exploring bearings of the rollers, it is necessary to remove the belt so as to determine their state.
After determining the condition of the timing belt and convinced of the need for its replacement, buy a valve cover gasket. Preference only original parts. When replacing gaskets in any case, do not use sealant. Also note the seals crankshaft and camshaft. If they show any signs of leaking oil, change them. No accident in the oil flow there, but when it hit the timing belt will accelerate wear. Seals also install without the use of sealant and choose only the original.
When replacing the timing belt, notice the pump. It also carefully inspect any for signs of leakage and check the condition of the bearing. Without removing the belt to determine the leakage pump is almost impossible, as it is bolted to the engine block and antifreeze drips for a short time evaporate. If the belt has been removed around the control holes have traces of antifreeze on the pump, replace it, as there is a risk that the flow of antifreeze will increase. Also, don't forget to check the drive belts. If they are on the inner side there are cracks, replace.
When purchasing a used vehicle ask when was the belt replaced, if not, definitely replace.
Every 9000 km change the timing belt and rollers. If the rollers are badly worn, you can replace them, but in this case there is no guarantee that they will hold the next 9000 km.