Let’s hear it for all the unsung heroes residing in the engine bay! Some of the biggest heroes are your drive belts. Let’s talk about belts, shall we? Sometimes they have to squeal and squeal before we know it. That horrible noise is usually the last sign your belt will give you before it breaks. Sometimes a car belt failure will cause a minor temporary problem such as your steering getting hard because your power steering pump won’t turn or it can be much more serious when your warning lights are flashing because your alternator isn’t turning. Both scenarios are the makings of a very bad day. Your engine cannot function properly without these belts.
What they do
The drive belts on your engine basically “drive” accessories that are bolted to or hung through mounts on your engine. What accessories do I mean? How about that power steering pump I mentioned earlier? Drive belts also turn that little electrical generator called an alternator. They also “bring life” to your air conditioning compressor. In some cases, a drive belt can be responsible for turning a cooling fan or even the water pump. All of these devices are essentially powered by the turning force of your engine via some type of belt. Drive belts are essential to most secondary engine systems.
types of belts
There are several different types of seat belts used in automobiles and motorcycles. We will talk about the serpentine, the V-belt and the toothed V-belts.
The serpentine belt is the most common type of belt used on most cars and trucks. These belts are called “serpentine” because, you guessed it, they are long and their path through the accessories is “snake-like.” This type of belt usually feeds a large number of accessories. They were designed to save space by connecting most, if not all, fixtures on the same plane, thus eliminating the need to stack or stagger fixtures one behind or one in front of the other. A serpentine belt is usually ribbed on one side and flat on the other. This helps the belt stay in place. Usually the grooved side contacts the grooved pulley of an accessory like your alternator. The flat side comes into contact with a smooth pulley, like an idler pulley, which we’ll talk about later. All belts are important, however I’m sure you can see how important this type of belt is because it can provide power to all of your engine accessories!
The V-belt is still used in modern cars. It is called a V-belt because its cross-sectional view resembles the letter V. V-belts are typically used to power a single accessory, such as your vehicle’s air conditioning compressor. They are quite simple and fit on a V-shaped pulley. They are sometimes used in pairs on trucks or other powerful vehicles.
The toothed V-belt is used in high torque applications. Torque is essentially “turning force”. They are also used in powerful engines and motorcycles. This type of belt has teeth that fit into the grooves of a toothed pulley.
pulleys
Pulleys basically allow a belt to change direction as it goes to another accessory. All belts must operate under a certain amount of tension or strain to properly rotate an accessory without slipping. How is the tension maintained? With an idler/tensioner pulley of course! This type of pulley is attached to a large powerful spring or strut type system. These pulleys create tension on the belt by pushing it down to tighten. This causes tension along the entire length of the belt, allowing it to “grab” the accessory pulleys. The same thing would happen if you were to push down on a belt at the point where your hand is halfway between two pulleys or accessories. The maintenance of your pulleys is just as important as the maintenance of your belts.
Common causes of failure
Belts usually fail because they are old, brittle, or rotten. They are very durable; however, engine heat is generally not kind to the rubber and plastic components in the engine bay. How do you check your belts? Well, if you have a multi-rib belt, like a serpentine belt, look for bits of rubber that are missing. Make sure there are no gaps between the ribs on the belt. For V-belts, look at the sidewalls of the belt. It should not be shiny or enameled. This indicates that the belt is slipping and probably does not have the correct tension.
Another cause of drive belt failure is faulty pulleys. They should spin smoothly and shouldn’t wobble at all. The pulley should not have grease coming off of it. If it does, the ball bearing seal could be broken. Ball bearings work best with the proper lubricant. Without it, a catastrophic failure of the pulley is imminent and it must be replaced as soon as possible. The pulley must not be able to move from front to back and must not “slip” on its axis.
The idler/tensioner pulleys must provide the correct amount of tension on the belt for the system to function properly. There is normally a tension indicator on the idler and it should be near the midpoint. It should not be on the “loose” part of the indicator. This means that the belt has stretched and needs to be replaced.
Changing your belts
The first step to correctly changing belts is to make sure that you can put on the new belt correctly. There is usually a label with a diagram of the routing path of the belt through the fittings. Look this up and make sure you understand the diagram. If you’re not lucky enough to have a diagram, grab a piece of paper and a pen and draw your own diagram. Label the accessories with letters such as “A” for alternator and “C” for compressor. This will help identify accessories and maintain proper orientation.
Next you need to find your idler/tensioner pulley. If there is only one pulley, obviously this is it. What you have to do is apply opposite force to the pulley. To do this, insert a ratchet or breaker bar into the square hole in the pulley. Sometimes this hole may not be a square, as is the case with many German cars. These cars may have a star-shaped hole in the center of the pulley, requiring a torx bit to be installed on the ratchet or breaker bar. So if the pulley pushes in one direction, you have to pull in the opposite direction. As you do this, you should feel a gradual but gentle release of tension on the pulley. Push or pull the idler until it stops. At this point you will see that the belt is quite loose. Hold the breaker bar or ratchet with one hand and remove the strap with the other. Once the belt is removed from the idler pulley, you can slowly release the opposite tension that you applied to the pulley. Continue by removing the belt from all other accessories.
If there is no idler pulley, as is the case with most V-belts, simply loosen one of the fittings. Most of the time, it will be your alternator. If you loosen the correct bolt, the alternator will simply spin on its axis. Once you move it in the right direction, the tension on the belt will decrease and you can simply take it off. If you have more than one belt, you may need to remove one of them first to make it easier to remove the other.
When you have removed the belts, take a look at the integrity of your pulleys. If a pulley is bad or you know it has a lot of miles on it, you should replace that as well.
To re-fasten the belt, take a look at the belt path using the diagram sticker or the diagram you drew. Remember, the grooved side of the belt is usually in contact with a grooved auxiliary pulley and the smooth side should contact the smooth side of your idler/tension pulley. Loop the belt around as many accessories as possible. Make sure the ribs on the belt fit into the ribs on the pulleys. It should sit completely flat on the pulley. You should now push or pull the idler pulley in the same way you used to remove the belt. Push or pull with one hand and buckle up with the other. Sometimes another set of hands comes in handy and makes the job easier. Once the belt is in place, slowly release the opposing tension on the idler/tensioner pulley.
For the V-belt, simply reattach the belt; apply voltage to the alternator using a switch or lever. Then tighten the bolt that was loosened during removal.
How often should you change your belts?
Well, the correct answer is to check your owner’s or service manual, as vehicle usage conditions vary greatly. I would definitely change most belts every 50,000 miles. If your climate and driving conditions are harsh, change the seat belts more frequently.
Changing the drive belts on your engine is relatively easy. Most of the problems occur when trying to access the seat belts. Sometimes you have to change them from above the engine and sometimes from below. If you complete this task yourself, you can definitely save a lot of money. The more you do it, the easier it will be. This is a task that you can complete in an hour or two on a Saturday morning.
We’ve all heard that horrible screeching sound of belts slipping. Take care of your ears and mine by properly maintaining your drive belts.