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Belts and Hoses Explained

Getting to know car belts and hoses!

Belts and hoses are essential to any vehicle because a series of belts and pulleys drive engine components such as the alternator, water pump, fan, power steering pump, air conditioning compressor and air injection pump. Hoses, on the other hand, transfer coolant, brake fluid and fuel throughout the vehicle. Over time, these may crack, rust or leak.

Timing belts

A timing belt, also known as a cam belt, is part of an internal combustion engine that controls the timing of the engines valves. These belts are toothed, reinforced belts used to drive the camshaft via a sprocket to a crankshaft. They ensure the synchronisation of the engine’s camshaft, crankshaft and distributor. Rubber timing belts are reinforced with fiber chords, to keep everything in the engine in sync. So why is this important? The crankshaft converts the vertical movement of the pistons into rotational energy that turns the wheels of the vehicle. The camshaft opens and closes the engine’s valves to allow air and gases in and out of the engine. The timing co-ordinates the movement of the two. Without it, the pistons and valves would make contact and damage the parts. This internal collision can cause engine wear at least, and at worst engine damage. Therefore, it is important to replace the timing belt every four years or 80 000 to 100 000 kilometers or, in newer vehicles, every 150 000 kilometers. The vehicle’s maintenance manual will provide manufacturer recommendations. Signs of belt wear: Stripped teeth (which leaves a smooth section of belt where the drive cog will slip) or delamination and unraveling of the fiber cores becoming visible.

Serpentine belts

These belts transfer power from the crankshaft to all the engine components. When this single belt breaks, it can cause damage to the engine through overheating, loss of charging or loss of power steering. Signs of belt wear: Cracking and splitting or when the belt starts slipping and squealing.

Coolant hoses

These are hoses that transfer antifreeze throughout the engine cooling system, including the radiator and the heater core. Signs of wear include cracking, splitting and brittle or soft spots. Signs of wear: Cracking, splitting and brittle or soft spots Cars are designed to run hot, but there is a limit. A combustion engine is most efficient at around 90 degrees celsius. But if an engine is allowed to get too hot, moving metal parts can actually start to melt and fuse together, causing internal engine problems and damage. All modern cars have an ingenious cooling system that use a chemical coolant, called antifreeze, and a series of pumps, hoses, thermostats and fans to keep the car at its optimal running temperature. But low coolant levels, cracked hoses, loose or broken belts, a leak in the radiator or even a loose or missing radiator cap can cause the vehicle to overheat and break down. Check hoses for cracks, leaks and loose connections. Hoses should be firm, never soft and malleable. Hoses suffer from a slow deterioration process called electrochemical degradation (ECD) that eats away at the rubber from the inside. The most vulnerable sections are where hoses connect to clamps and secured to the radiator or the engine. Belts can also be visually checked for cracks and damage. If the belt looks excessively slick or smooth then it needs to be replaced. Experts say the risk of belt failure rises dramatically after 50 000 to 60 000 kilometers.


Sooner or later your vehicle engine’s drive belts and coolant hoses will start to dry out and crack. Over time, belts and hoses lose their ability to properly expand and contract due to repeated heat and cooling as well extreme ambient temperature during winter and summer. One sudden malfunction of these relatively inexpensive but very important parts can have costly consequences. Simply visit your nearest AutoZone store or contact our Technical Team on 0800 200 990 to help you avoid this kind of breakdown with advice on oil changes, brake and shock absorber changes, preventive car maintenance and belt and hose replacement. Our experienced staff can advise you on many potential belt and hose problems by guiding you through a simple visual inspection. Regular inspections, coupled with timely belt and hose replacement in accordance with your vehicle’s manufacturer recommendations will help prevent breakdowns and protect against expensive repairs.