Many of your engines’ critical components are driven by belts. Belts operate in tough conditions such as high heat, high speed and considerable tension. Since rubber is an unpredictable material even under ideal conditions, belt failure is one of the most common causes of breakdown on the road.
Luckily belts are easy to check, and replacing them at home is relatively easy and inexpensive. We’ll show you how.
Most modern vehicles use one or two V-rib drivebelts that drive the water pump, alternator, air conditioning compressor and other components. While these belts are very reliable, failure usually makes the vehicle undriveable. So, it’s important to make sure your belts are in good shape and tensioned properly.
How to tell when a drivebelt needs replacing
Belts should be flexible and not shiny, which indicates slippage. Look closely at the belt for signs of cracking. Also check that there are no oil or coolant leaks that can get on the belt.
If you hear a squealing noise like this, especially at start up or when you turn on the AC, you’ve got a slipping belt. This can be caused by something as simple as the belt being too loose, but more likely it is just so old, hardened or contaminated that it will no longer grip properly.
Most recent vehicles use a spring-loaded tensioner to automatically maintain the correct belt tension. On some older vehicles the tension may need to be manually adjusted.
To replace most belts all you need to do is pry the spring-loaded tensioner away from the belt and pull the belt out from among the pulleys. Since the routing of the drivebelt is critical, be sure you have a diagram handy. The diagram is usually on a sticker in the engine compartment. If your vehicle does not have a sticker, make a diagram before taking the old belt off.
With proper routing confirmed, pry the tensioner again and put the belt into place over the last pulley. Be sure the belt is riding in the center of all the pulleys and not off to one side.
On vehicles with manually adjusted belts, you’ll need to loosen a component, and pivot or slide it to release the belt tension. On this type of belt, you need to pry the component away from the engine, or crank the adjuster bolt, to get the proper tension, then tighten the bolts. The general rule of thumb is to leave the belt loose enough so the longest section can be twisted 90 degrees.
How long should a drivebelt last?
Typically, if there are no oil or coolant leaks degrading them, modern rubber belts will easily last 50 or 100,000 miles.
But you should inspect them every 30,000 miles for cracking, contamination, fraying, or loosening of tension.