Reasons Your Car Overheats, But Only When Idling - Service Information at Mike Shaw Subaru

The radiator is a crucial part of your car that helps keep the engine from running too hot and sustaining damage. It's located behind the front grille of the car, so that air can pass across the radiator as you drive. If not enough air flows across the radiator, the engine will get too hot and the engine temperature warning light will come on in your dash. This is not a warning to be taken lightly! Overheating engines can quickly sustain serious damage, even destroying themselves entirely in some cases.

If your car only overheats when it's idling, it could be because of one of these three common causes of engine overheating. But no matter what's causing your car to get a little hot under the collar, you'll want an expert team to help fix it -- before it can ruin the engine completely. Learn more from the Mike Shaw Subaru service experts below!

This vehicle's temperature gauge is in the red, indicating a dangerous overheat condition

3. Engine Needs A Coolant Flush

To keep the engine cool, coolant (aka antifreeze) circulates through the engine, drawing heat away from its hottest moving parts. This helps to keep the engine operating at its ideal operating temperature.

Over time, the coolant will pickup small particles like rust and corrosion, and the system will need to be flushed out, and new coolant added in. If there's too much particulate in the coolant, it can affect cooling performance. It could even cause your engine to run too hot when sitting at a light or idling away in a drive-through line.

 
A technician pours bright-green coolant, also called antifreeze, into this car's cooling system

2. Stuck Thermostat

The cooling system helps keep the engine from getting too hot, but the engine does need to warm up a bit to achieve optimal performance and efficiency. When you first start your car, and the engine is cold, a small component called a thermostat stays closed, so coolant isn't flowing throughout the whole system. Once the engine reaches its ideal temp, the thermostat opens so coolant can flow and the engine stays at that temperature.

The thermostat can become stuck closed, or might only open partially, causing your cooling system to underperform. There might be sufficient cooling taking place when the car is in motion, but, once stopped, the engine could get too hot. You'll want to have a new thermostat installed that opens and closes reliably.

Steam rises from the top of this engine, indicating that it's dangerously overheated

1. Failing Radiator Fans

Remember, airflow over the radiator is what reduces the temperature of the coolant in the cooling system so that it can be recirculated back to the engine and draw away more heat. This cycle is constantly taking place as you drive -- but, if you're sitting still at a stoplight or barely moving in bumper-to-bumper traffic, there might not be enough forward motion to force airflow across the radiator.

That's where the radiator fans come in. When idling or moving slowly, these fans blow air over the radiator so that the cooling system continues to work well, even when the vehicle is stopped. However, if they've stopped working because the fan motor burned out, an electrical short has cut off the power supply to the fans, or because debris got lodged in the fan itself, your engine could start to overheat! But, once you start driving, the motion of your car forces air over the radiator, bringing the temperature of the engine back down again.

One more thing you should remember: engines only need to be overheating for a few minutes to cause serious damage to occur. Even if your car only overheats intermittently, we think it's best to stop driving the car, let the engine cool and then have it towed to Mike Shaw Subaru in Thornton for an expert diagnosis and a quality repair.

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  1. Mike Shaw Subaru

    1650 W 104th Avenue
    Thornton, CO 80234

    • Sales: (888) 472-4482

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Mike Shaw Subaru

1650 W 104th Avenue
Directions Thornton, CO 80234

  • Sales: 720-724-9280
  • Service: 303-729-2683
  • Parts: 720-728-0862