Preparing Your Fleet Vehicles for Hot-weather Driving

As temperatures increase during summer months, the demand placed on motor vehicles (and their engines in particular) increases significantly, elevating the risk of engine failure. Engines rely on mechanical tolerances to produce power, oil to keep the contact surfaces separated, and coolant flowing through the engine to the radiator for cooling. Should any one of these critical elements fail, then engine failure is imminent. 

Mechanical tolerances 

Signs of worn engine components can normally be heard in the form of knocking, grinding or squealing noises because of metal components colliding or rubbing. By design, no rotating metallic parts are designed to collide or rub together. Therefore, when sounds like these are present, it is time to have your engine checked by a mechanic. 

Oil 

There are many different types of engine oil. The correct oil for your engine will depend on its type and ambient temperatures. 

Petrol engines can subject the engine oil to temperatures of up to 160°C. Choosing the right oil depends on the cold start temperatures, as the correct oil will sufficiently lubricate the engine at ambient temperature and when it reaches normal operating temperature. The method for selecting the correct oil is to refer to the viscosity rating on the packaging and ensure that the oil operating temperature range is within the ambient temperature range. 

Diesel engines rely on the compression of diesel fuel and oxygen to a point where the pressure is so great that combustion occurs. This exposes the engine oil to temperatures of up to 315°C. Diesel fuel is not as pure as petrol and contains more contaminants. Diesel engine oil is designed to deal with the higher compression and generally contains more detergents to assist in removing impurities left behind by the diesel fuel. 

Cooling system 

Coolant 

Healthy coolant is free of minerals, non-acidic, and contains anti-iodising agents to prevent corrosion and lower the freezing temperature. However, coolant degrades over time and may require replacement. Follow the owner's manual for recommendations on how frequently it should be changed. Never mix different types of coolants, as this can lead to chemical reactions and damage to the cooling system. 

Cooling systems rely on pressure to increase the boiling temperature of the coolant. The higher the pressure, the higher the temperature before the coolant starts to boil. For this reason, the radiator or coolant reservoir should never be opened while the engine is hot, as the pressurised coolant can cause serious burns. 

Should a leak develop in the cooling system, it presents two issues. First, the loss of coolant will introduce air into the system, which acts as an insulator and prevents heat from being transferred to the radiator. Second, the leak will lead to a loss in pressure, lowering the boiling point and causing further complications. 

Your mechanic can conduct a cooling system pressure test to ensure that there are no leaks and that the system can hold pressure. 

Water pump 

The water pump is vital for pumping coolant around the engine and into the radiator. It is normally powered by a belt driven from the engine's crankshaft. For this reason, all belts should be checked for condition to ensure they are free of cracks and tight enough not to slip. Your mechanic should check noisy or leaking water pumps as soon as possible. 

Radiator 

The radiator is critical for transferring heat from the coolant into the air. For this process to take place, radiators require good airflow across the fins. The radiator needs to be cleaned regularly to eliminate the build-up of dust and other foreign objects that prevent the air from flowing over the fins. Lastly, the radiator may look clean from the outside but be partially blocked on the inside. Part of the vehicle's regular maintenance programme should include a radiator flush to ensure the coolant can flow freely. 

Cooling fan 

A fan cools the radiator. Some vehicles use a fan driven by the engine, some use an electric thermo fan, and some use both. When the vehicle is stationary or travelling at low speed, the fan provides the necessary airflow over the radiator fins to cool it. Should the fan fail or the airflow ducts become blocked, the vehicle should be checked by a mechanic as soon as possible. 

Thermostat 

Often forgotten, the thermostat plays a critical part in the engine cooling system and engine performance. Since engines work more efficiently at normal operating temperatures, the thermostat's job is to prevent the coolant from leaving the engine block until the operating temperature is reached. Once the temperature is reached, the hot coolant flows to the radiator, and the cooler coolant flows into the engine block, providing cooling while the hot coolant cools in the radiator. This cycle continues at a steady pace while the engine is running to maintain a constant temperature and allow time for the coolant to cool in the radiator. 

A thermostat may fail in the open position, which means the coolant continually flows through the engine clock. Radiation increases the time for the engine to warm up and decreases the time that the coolant must cool in the radiator. This leads to a slow, constant increase in temperature, which, on hot days, eventually leads to an overheating situation. 

Alternatively, thermostats can fail in the closed position, preventing the coolant from leaving the engine block and resulting in rapid overheating. 

Battery life 

Another common misconception among drivers is the effects of weather on batteries. Although cold weather does have adverse effects on batteries, heat can be more destructive. Whereas the average car battery lasts three to three and a half years, batteries in vehicles exposed to continuous high temperatures tend to last less. 

Simple steps to help prolong your battery's life can include: 

• Cleaning the battery. Dirt can quickly build up, especially in rough desert terrains, and this will result in draining the power in the battery. Use a wire brush to clean the terminals and baking soda dissolved in water to clean the battery itself. 
• For larger, heavier vehicles that require batteries to be refilled with water, check the levels regularly -- especially during the summer months -- and, where possible, refill with distilled water.