Changing a timing belt is not an easy job. It will require the average back yard do-it-yourself a full weekend to remove all of the parts necessary to reach the timing belt. If you're not confident, or if you can't spare more than one weekend if the job takes longer than expected, you might be better off taking the car to a mechanic.

You should plan on changing a timing belt or chain whenever it is easily accessible for other jobs, such as a water pump replacement. Plan on changing the timing belt if your car has accumulated more than 60,000 miles. Worn or damaged timing belts can cause the engine to run rough or, even worse, not run at all. In fact, a timing belt break can be catastrophic for the engine. Worn timing belts can cause decreased power and fuel mileage as well. Since it's so difficult to check the wear on a timing belt because access is difficult, plan to change the belt at recommended intervals. It's preventative maintenance that will pay big dividends in the future.

As every car is a little bit different, it is impossible to detail the requirements for every car. However, here is a general guide as to what you can expect to have to do when replacing a timing belt. I highly recommend buying the appropriate Hayne's Manual for you car at an auto supply store. It's a great reference that includes step by step instructions and helpful pictures.

Indications: When and why should I change it?

1. Wait overnight for the engine to cool off. It's not worth it to risk burning yourself on the engine, which stays hot for a long time!

    

2. Disconnect the battery and chock the wheels so that the car cannot roll.
3. Remove all obstructions to the timing belt cover: This can take a while, as there are usually quite a few things in the way. Here's a list of a few common pieces you'll have to remove:
   • Remove the air intake assembly.

      

   • Loosen the pulley that powers the water pump, if necessary. Some cars require your to remove other equipment such as the power steering pump. If so, remove the belt from the pulley, and unbolt the pump. Move it back out of the way.
   • Remove any other accessories that interfere with access to the timing belt.
4. Use a large wrench on the crankshaft pulley to align the mark on the crankshaft pulley with the 0 on the timing scale molded into the engine block.
5. Remove the timing belt cover bolts and pull the cover off.
6. Check the tensioner bearings. Replace them if they are loose or noisy.
7. Check the camshaft and crankshaft seals. If they leak, it could cause premature failure of the new timing belt. Replace them if necessary.
8. Make sure that all timing marks are properly aligned, then loosen the timing belt tensioner and remove the timing belt. Do not allow either the camshaft or crankshaft to move while the belt is off.
9. Put the new belt in place. Adjust the tension, if necessary. Make sure that it sits well over the teeth of the timing sprockets. Don't over-tighten.
10. Apply a new gasket to the timing belt cover and replace it.
11. Reinstall all of the accessory pumps that you took off earlier, including the water pump. Many mechanics recommend replacing the water pump while you have it off. It's up to you.
12. Check that all timing marks are still properly aligned.
13. Reinstall the air intake assembly.
14. Reconnect the battery.
15. Start the engine and listen carefully to how it runs. You shouldn't hear any loud knocks if the timing is still correct.

If you allowed the timing to become misaligned while you changed the belt, you have a serious problem on your hands. Either correct the error, or consult a mechanic. Do not operate a vehicle with incorrect timing, as serious internal engine damage could occur.