Drive Belts

There is a lot of confusion today about drive belts, and when to replace them. First it needs to be determined what type of belt is on the vehicle. There are three different belts. The first design is the V belt. This picture gives a cross section view. (If you have a riding lawn mower take a look at the belts, they are the same.) A good rule of thumb is to replace this belt every four years or 40,000 miles. Take a look at the inside of this belt for cracks. Small cracks are normal but if any cracks go halfway through the belt or more then replace it.

The next belt is called a serpentine belt. This belt is flat and has several grooves on one side. It runs several components on the engine with only one belt. Most vehicles only have one or two of these belts on the engine and they last a lot longer than the V belt. The serpentine belt can be made out of two different types of materials. One is an EPDM material and should last the life of the vehicle. It is extremely rare to observe any cracks in EPDM belts and it is not expected that they will require maintenance before 10 years or 240,000 km (150,000 miles) of use. Older style belts, which were manufactured with a chloroprene compound, may exhibit cracks depending on age. However, the onset of cracking typically signals that the belt is only about halfway through its usable life. A good rule of thumb for chloroprene-based belts is that if cracks are observed 3 mm (1/8 in) apart, ALL AROUND THE BELT, the belt may be reaching the end of its serviceable life and should be considered a candidate for changing. Small cracks spaced farther apart should not warrant replacing the belt.

Any belt that exhibits chunking (small pieces of rubber missing in the grooves) should be replaced.

A broken belt is always bad news because when it snaps, all drive power to whatever it turns is lost. That means the water pump quits circulating coolant through the engine, the alternator quits producing amps, the power steering pump ceases to assist steering, and the air conditioner quits cooling. Many newer vehicles have a single serpentine belt that drives all of the engine's accessories, so when it fails everything stops working.

The other belt is called a timing belt. Not all engines have one so check the owner’s manual to make sure. This particular belt cannot be seen because it is hidden behind covers on the engine. The timing belt is made out of different types of rubber material as well and needs to be replaced according to the schedule in the owner’s manual. Certain engines can be damaged from the timing belt breaking and can leave a motorist stranded.