If you're not a car enthusiast, you've probably never heard of a timing belt tensioner. However, these little parts play a big role in the way your car runs. If you don't take good care of your car's timing belt tensioner, you can wind up with some very expensive repair bills later.

But in order to understand how important these parts are, you have to start by understanding what a timing belt is.

Under your hood, timing belts are responsible for controlling the timing of your engine's valves. As you drive down the road, your valves open and close. But to make your engine work correctly, they have to open and close at a particular rhythm. If they're not synched up properly, your valves can open at the wrong time, crash into the pistons, and cause some big problems. Your timing belt will make sure that your valves open and close when they are supposed to.

But since your timing belt has so much responsibility, it can't do all of the work all by itself. That's why your car comes with a timing belt tensioner - to make sure that your belt keeps moving at the correct pace. As long as your belt is moving along at the right speed, your valves will open and close properly, and everything will run smoothly. Your tensioner has a spring on it that puts pressure on the belt to keep it working the way it should.

Like all car parts, though, your timing belt tensioner will not last forever. Luckily, you will not have to replace it as often as you do other parts - but you do need to make sure that it gets the attention it needs. Usually, a timing belt tensioner can last 60,000 miles or so, depending on what kind of car you have and how old it is.

Two of the world's most common tensioners - Honda timing belt tensioners and Toyota timing belt tensioners - come with some handy guidelines to help you know when to replace them.

When it comes to Honda timing belt tensioners, how you take care of them depends on your model year. If your Honda was made before 1989, you will need to replace the tensioner every 60,000 miles. If your Honda was made between 1990 and 1996, you will need to replace the tensioner every 90,000 miles. If your Honda was made after 1997, you can go at least 100,000 miles before you need to replace it.

Similarly, Toyota also says that your car's age will determine when you change your timing belt tensioner. Older Toyota's need theirs replaced sooner - about every 60,000 miles - while newer Toyota timing belt tensioners can last longer - about 90,000 miles - before they need to be changed.

When you do replace it, how much will a timing belt tensioner cost?

The actual tensioner itself is not that expensive. Usually, you can expect to pay $50-$150 for one, depending on what kind of car you have. But, remember, you will also need to factor labor time into the total cost. Unless you have a lot of experience working on cars, you need to let a pro handle this work. Replacing a tensioner is tricky - and it's not a job for amateurs!

However, you may be able to cut down on some of the labor costs by combining your tensioner work with other projects. In fact, many people replace their tensioner, their timing belts, and their water pump all at the same time so that they only need to pay someone to dig around inside their engine one time.

Unfortunately, though, your timing belt tensioner may not adhere to that schedule. If you start to notice problems with it, you can't afford to wait; you need to get it looked at ASAP.

How do you know if there's something wrong with your tensioner?

1. You could hear strange noises

If your tensioner is cracked, you will likely hear a rattling when you start the car or step on the gas. If you're hearing a humming noise, it could mean that the bearings on your tensioner are worn out. Or, if you hear a screech or a squeal when you change gears, it could be a sign that there's too much pressure on the tensioner.

2. You notice big changes in your RPM's for no apparent reason

If you are traveling at a low speed and your RPM's are all over the place, your tensioner could be to blame. If the timing belt isn't keeping the valves in sync, your engine will not be able to shift smoothly.

3. You're seeing leaks

If you see oil leaking out around your crankshaft, it could be due to a crack in your tensioner. Or, if you see grease leaking around the area, ask a pro to take a look. It could be coming from your tensioner - meaning that there could be too much friction inside, which will cause your tensioner to wear out.

Be sure to browse the rest of this site for information on timing belt replacement costs and much more.