Fleet Heat

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High outdoor temperatures can wreak havoc on your vehicles’ mechanical and electrical systems. Make sure your fleet is summer road ready.

July 1, 2022

The hotter the weather, the harder a service vehicle works. This increases vehicle wear and tear and the potential for breakdowns, costing you time, money and customers.

“Extreme heat causes a great deal of stress on any kind of [vehicle] system,” said Duston Maynes, a Los Angeles-based operations manager for RepairSmith, which provides on-site maintenance and repair of fleet and consumer vehicles.

He identified some common heat-related issues and how to overcome them.

ENGINE COOLING SYSTEM. The engine cooling system (radiator, thermostat, water pump, hoses and coolant/antifreeze) works overtime in extreme heat. “As the temperature increases and the humidity increases, your pressures will go up, and this strains the system a lot more,” said Maynes. Higher pressure causes seals, hoses and connections to leak and break. As a result, engines can overheat.

To help prevent this, flush the engine coolant every 30,000-40,000 miles. Consider using a mixture of coolant and water, which can be more efficient at cooling than coolant/antifreeze. Also make sure the radiator is unobstructed and clear of dust and debris.

AIR CONDITIONING. Similarly, high heat can increase pressure in the air conditioning system, causing hoses and components to leak or break. To reduce the strain, do “anything you can do to keep the cabin temperature down” so the air conditioning doesn’t have to work as hard to cool it, said Maynes. This includes tinting windows, using sunshades and parking in shade whenever possible. (This also will protect sensitive electronics such as GPS and cameras from the stress of extreme heat.)

BATTERY. A higher temperature “really kills batteries,” said Maynes. According to the RepairSmith website, the internal temperature of a lead-acid battery on a hot day can reach more than 140 degrees Fahrenheit, far above the ideal operating temperature of 80 degrees. For every 15- degree increase in ambient temperature, the battery life cycle is cut nearly in half.

Lead-acid batteries generate power through a chemical reaction that requires water, and high temperatures can cause that water to evaporate. This reduces the battery’s ability to hold a charge or start an engine. Additional stress is put on batteries when air conditioning and engine cooling systems are working overtime.

It’s best to replace a battery before it fails, which usually happens when the temperature drops, said Maynes. You may have to change the battery every two to three years, despite what the manufacturer says.

OIL. “Extreme heat will break down your oil a lot faster,” said Maynes. It reduces the oil’s viscosity (its ability to flow), making it “sticky, and that can then start gumming up components,” he said. The vehicle may lose horsepower, get lower mileage and have engine components that experience increased wear and tear. Basically, the engine works harder and wears faster, potentially failing.

Maynes recommended changing the oil more frequently than the interval stated in the service manual.

TIRES. As temperatures rise, so does tire pressure. According to the RepairSmith website, tire pressure increases about one pound per square inch (psi) for every 10-degree Fahrenheit increase in temperature. This causes tires to become overinflated, increasing your risk of blowouts and excessive tread wear. High heat and sun also dry out the rubber, making it less flexible. “Tires get hard, and they get microcracks,” said Maynes. This makes for a less comfortable ride and a higher chance of blowouts. Excessive heat also causes roads to crack and buckle, which increases the hazards that cause flat tires.

Monitor tire pressure regularly and adjust it accordingly. Also, inspect for microcracks and replace tires as needed, which may be sooner than you expect.

GASOLINE. Extreme heat may cause the mixture of air and gasoline to ignite prematurely in the engine, which reduces a vehicle’s fuel economy. You may notice a pinging or knocking when this occurs. This can damage spark plugs and potentially pistons and piston rings. High temperatures also increase pressure in the gas tank, which puts stress on tank components and seals.

Maynes advised driving with a full tank, or not less than a quarter tank, to dissipate heat and protect tank components. “The fuel acts as a coolant for that fuel pump inside the tank,” he said.

EV/HYBRID BATTERIES. “In the electric vehicles, extreme heat affects the battery range,” said Maynes. This means you won’t be able to drive as far without recharging, especially if you’re trying to cool the cabin while you drive. This alone can result in losing up to 30 miles of range, he said.

Maynes suggested using the pre-trip function on the vehicle app to adjust cab temperature while the vehicle is on charge and before getting behind the wheel.

LAST THOUGHT. To help prevent breakdowns in extreme heat, have a trained mechanic inspect service vehicles regularly to identify heat-related wear and tear, change fluids and perform preventive maintenance.