How hot will it get this summer? The highest recorded temperature in Illinois was 117 degrees in 1954. But that was in East St. Louis, not in McHenry. The question to ask is how your car, truck or SUV would stand up to that kind of heat.

The average temperatures in Illinois during June, July and August are 71.8, 75.3 and 73.5 degrees, respectively. But that’s average temperature that includes night-time lows. Day-time highs are higher than that.

What we know for sure is that, over the course of the summer, we will see multiple days in the 90s. We’re liable to see days in the 100s. But even days in the 80s will test your car, truck of SUV’s cooling system.

The cooling system includes the coolant, that liquid poured into the coolant reservoir. It includes the radiator. It includes hoses that move the coolant from the engine to the radiator and back again (after air has passed through the fins of the radiator cooling the coolant inside).

The cooling system also includes a thermostat that regulates when the passage of coolant is stopped. This happens, for instance, when the engine is cold so that the coolant warms up quickly to the operating temperature.

The cooling system also includes the fan(s) that pull the air through the radiator to carry away heat from the coolant, heat that the coolant carried out of the engine. It includes passageways in the engine block and heads that allow the coolant to flow through the engine collecting the heat and a water pump that drives the coolant along the way.

On hotter days, the air that is pulled through the radiator is already hot. The hotter the air, the higher the heat in the coolant that is collected by the passing air. In other words, hotter air has less capacity for collecting heat from the coolant.

All of the parts described above need to work in concert to continue pulling the heat out of your engine. The combustion engine in your car runs at a normal operating temperature of between 195 and 220 degrees.

As the engine moves above those temperatures, the heat builds pressure in the coolant. Now you’re testing your cooling system for week spots in the radiator, hoses, clamps, gaskets, etc. If something might give, on a really hot day, there’s a good chance that it will.

If the coolant is old and lacks its expected capacity for carrying away heat, or if your car, truck or SUV is low on coolant, that’s a problem waiting to happen. If the thermostat is stuck closed. You’ll soon overheat the engine. If the radiator is clogged or leaking, expect a long hot day. These are some of the ways that your cooling system could let you down on a particularly hot day, or even a day that isn’t extraordinarily hot. 

The solution is to have your cooling system checked, top to bottom, to make sure it’s in good working condition. And the best time to check your cooling system is at the beginning of summer, before you’re caught on a particularly hot McHenry day with a cooling system that can’t handle it.