When does the timing belt need to be replaced

A timing belt runs the engine camshaft (or camshafts in a dual-cam engine). It's called timing belt because its main job is to precisely time valve opening and closing with up-and-down movement of the pistons. Timing belt replacement is one of the high-price maintenance items that many motorists have to deal with. How often does the timing belt need to be replaced?
Timing Belt Timing belt.
Timing belt recommended replacement intervals vary from 60,000 to 106,000 miles. You can find the recommended interval in your car's maintenance schedule. We posted several links where you can check the maintenance schedule online at the bottom of this post.

Can a timing belt last past the recommended interval? Yes, in some cases. We came across a number of high-mileage cars with a timing belt that has never been changed. In fact, as we worked on this article, we discussed the Toyota Highlander belonging to one of our colleagues. It had almost 200K miles and the timing belt has never been changed. "I'll just keep checking the belt condition; it still looks OK" – was the owner's response.

On the other hand, there are many cases when a timing belt breaks at a lower mileage than the recommended interval. Usually, premature timing belt failure is caused by faulty belt hardware (tensioner and idlers), leaking water pumps, improper tension and when a timing belt is soaked in engine oil. How can you tell if the belt is in good shape or needs to be replaced as soon as possible?
Can a timing belt condition be inspected? The answer is yes. Can you see the timing belt under the hood? No, a timing belt is usually covered by plastic or metal covers. Your mechanic can remove one of the covers and visually assess the condition of the timing belt. For example, this timing belt in the next photo belongs to the Acura TL with 52,000 miles. The owner wanted to check the timing belt condition before going on a long road trip. According to the mechanic, this belt is in a good shape and can last for a while longer.
Timing Belt condition This timing belt is still in good shape.
The timing belt in the photo below belongs to a Toyota Celica with 150,000 miles. The engine was still running fine, but upon the inspection, the mechanic found that the timing belt is in poor shape (you can see many cracks). The owner rightfully decided to have it replaced.

What happens if a timing belt breaks? There are two types of engines: an interference and non-interference. In an interference engine, if a timing belt breaks while driving, there is a good chance that the engine might be severely damaged. A non-interference engine will stall if a timing belt breaks, but further damage might be limited. The difference is that in an interference engine, valves that are fully open will be hit by the piston as it travels to its top position. In a non-interference engine, there is still some clearance between fully open valves and a piston in the top position.

How to know if your engine is an interference engine? Here is the link to Timing Belt Replacement Interval Guide, courtesy of Gates corporation. In this guide, the interference engines are marked with the star sign. Another reason to replace the old timing belt is that over time it stretches. As a result, the engine timing might become too retarded (delayed).
Cracked timing belt This timing belt is in a very bad shape.
Symptoms of a retarded engine timing include lack of power and slow pick-up. In some cars, a stretched timing belt can also produce a dull rattling noise coming from the timing belt area. Usually the noise is noticeable at idle, but disappears when the engine is revved.

How much does the timing belt replacement cost? It depends on the engine. Timing belt replacement in a 4-cylinder engine may cost from $250 to $600, plus a little extra if you want to replace the water pump and other hardware. In a V6 or V8 engine, the timing belt replacement cost can run from $380 to $780.
Is it necessary to replace a water pump, as well as timing belt tensioner and other hardware along with the belt? It's not necessary, however, it's usually recommended, because very little extra labor is involved in replacement of additional parts. Water pumps do wear over time, so it might make sense to replace the water pump along with the belt.

Do all cars have a timing belt? The answer is no, many modern cars have a timing chain instead. A timing chain is a maintenance-free unit and rarely need replacement. Read more: When a timing chain needs to be replaced.
How to know if a car has a timing chain or belt? First, you can check your maintenance schedule or call your dealer.
Another option is to ask your mechanic during your next oil change. Some car manufacturers publish the list of models that have a timing belt online; for example, here is the Toyota list: Does my vehicle have a timing belt or timing chain? The Gates Timing Belt Replacement Interval Guide we mentioned before has a list of cars that have a timing belt. Of course, you can always google: '2007 Honda Accord V6 timing belt or chain?' Is it difficult to replace a timing belt as a DIY project? If you have the tools and the skills, it's not that difficult. In a small 4-cylinder engine, for example, in Toyota Tercel, it can be done within two hours. The hard part is usually the removal of the harmonic balancer (main engine pulley) as the bolt holding it is very tight and sometimes you might need a special puller to take the pulley out. Another difficult task is to set the timing properly and adjust the belt tension when the new belt is installed. For this you might need the factory service manual.