CDL: Driving in Very Hot Weather
Driving in Very Hot Weather
Extreme heat puts extra strain on nearly every system in a commercial vehicle — tires, engine, cooling system, belts, and hoses all work harder when temperatures climb. This article covers the pre-trip checks worth paying special attention to in hot conditions, and the driving adjustments that help prevent overheating and tire failure.
Vehicle Checks Before Driving in the Heat
Your pre-trip inspection in hot weather should follow the same basic routine you'd use any other day, but a handful of items deserve closer attention.
Tires
Check both the mounting and the air pressure of every tire, and plan to inspect them again roughly every two hours or every 100 miles while driving in very hot conditions. Keep in mind that air pressure naturally rises as temperature increases — don't release air to bring pressure back down, or the tires will end up underinflated once they cool off again. If a tire is too hot to touch, don't keep driving on it. Stay stopped until it has had a chance to cool, since continuing to drive on an overheated tire risks a blowout or even a fire.
Engine Oil
Engine oil does double duty in hot weather — it lubricates moving parts and also helps keep the engine cool. Make sure the oil level is adequate before setting out, and if your vehicle has an oil temperature gauge, keep an eye on it throughout the drive to confirm it stays within the proper range.
Engine Coolant
Before starting your trip, confirm the cooling system has enough water and antifreeze based on the engine manufacturer's specifications — antifreeze isn't just for winter; it helps protect the engine in hot conditions as well. While driving, check the coolant temperature gauge periodically to make sure it stays in the normal range. If the gauge climbs above the highest safe reading, something may be wrong and could lead to engine failure or even fire. Stop as soon as it's safe to do so and investigate.
Some vehicles have sight glasses or see-through coolant overflow and recovery containers, which let you check the coolant level even while the engine is still hot. If the container isn't part of the pressurized system, its cap can be safely removed and coolant added even at operating temperature.
Never remove a pressurized radiator cap on a hot engine
Never take off the radiator cap or any part of the pressurized cooling system until the engine has cooled. Steam and boiling water can spray out under pressure and cause serious burns. A simple test: if you can comfortably touch the radiator cap with your bare hand, it's probably cool enough to open.
If you need to add coolant to a system that doesn't have a recovery or overflow tank, follow these steps in order:
- Shut the engine off.
- Wait until the engine has cooled.
- Protect your hands with gloves or a thick cloth.
- Turn the radiator cap slowly to the first stop, which releases the pressure seal.
- Step back while the pressure releases from the cooling system.
- Once all pressure has been released, press down on the cap and turn it further to remove it.
- Check the coolant level visually and add more if needed.
- Replace the cap and turn it all the way to the closed position.
Engine Belts
Learn how to test the tightness of your vehicle's v-belts by pressing on them. Belts that are too loose won't turn the water pump or fan properly, which leads directly to overheating. While you're at it, check for cracking or other visible signs of wear.
Hoses
Make sure every coolant hose is in good condition. A hose that fails while you're driving can lead to engine failure — and potentially fire.
Driving Adjustments for Hot Weather
Watch for Bleeding Tar
In very hot weather, tar in the pavement can rise to the surface, and any spot where this "bleeding" happens becomes extremely slippery. Stay alert for these patches, especially on older or poorly maintained roads.
Slow Down to Prevent Overheating
Higher speeds generate more heat, both for your tires and your engine. In desert conditions especially, that extra heat can build to dangerous levels, raising the risk of tire failure, tire fire, or engine failure. Driving at a more moderate speed in extreme heat isn't just about comfort — it's a real safety measure.
Extreme heat doesn't cause dramatic, sudden failures out of nowhere — it wears down systems that were already close to their limits. A careful pre-trip inspection, regular monitoring of your gauges and tires while driving, and a willingness to slow down when conditions call for it are what keep a hot-weather trip from turning into a roadside emergency.