Why is My Car Overheating With Full Coolant?

When that temperature gauge begins to climb to a worrying level, most people immediately assume they must have a coolant leak; and in a large portion of circumstances, this is the correct assumption. However, a lack of coolant isn’t the only thing that can lead to dangerous heat buildup.

Other Possible Causes of Overheating

Though checking coolant levels should be your starting point for diagnosing overheating, it’s important to understand the other portions of your vehicle that could prevent proper cooling.

You should never open your coolant reservoir to check while the vehicle is warm from driving, as the cooling system is pressurized and may spray boiling coolant over you and the engine. Instead, let the vehicle cool down completely before checking. 

Faulty Water Pump

Sufficient coolant levels don’t do much good when that coolant isn’t moving through the system. The water pump’s job is to keep coolant flowing from the radiator through the rest of the system and generally sits at the front of the engine. This is not only a common point for a coolant leak to develop, but it’s also possible that your pump could fail even with enough antifreeze. 

A bearing or impeller failure could prevent your pump from moving coolant, and as the fluid sits, the engine will be running without it. As the pump is driven from the accessory belt, a bad belt or tensioner could also result in an inactive water pump. 

Broken Thermostat

Your thermostat is responsible for regulating the volume of coolant sent through the system. Over time these thermostats can fail for a variety of reasons, from wiring defects to damage from unrelated issues. When the vehicle is unable to control the amount of coolant, it could leak to overheating. 

Blocked Radiator

While coolant is great at absorbing heat from your engine, it needs a large surface area to disperse that heat from the vehicle. This is where the radiator comes into play, which runs coolant between many little fins as outside air rushes over. Ensuring the radiator has proper access to air is crucial, as the radiator won’t be able to effectively disperse the coolant’s thermal energy without it.

As the radiator sits at the front of the vehicle in most cases, with just a grill and fan to protect it, it’s possible for leaves, bugs, dirt, and other debris to cake the front of the radiator and block sufficient air from passing through. Luckily, it’s easy to visually check your radiator for blockages, since it sits in a very visible position behind your front bumper on most vehicles. 

Clogged Heater Core

Rather than using energy to generate its heat for keeping the cabin warm, heater systems draw it from hot coolant before passing through the radiator again. A small amount of coolant will be diverted from the engine through a small radiator called the heater core. From there, the heater fan blows the warm air from the coolant into the interior. 

In some vehicles, specifically ones where coolant is always diverted to the heater core no matter if it’s in use, a buildup of contaminants and debris can create a blockage within the narrow hoses and channels. This obstruction will prevent proper coolant flow, or lead to leakage within the HVAC system. A common sign of a clogged heater core is lukewarm air from your vents while the heat is cranked up. 

Broken Cooling Fans

Though radiators receive enough airflow naturally during driving, they require a cooling fan that kicks in while the vehicle is idling or reaches a specific temperature. There are various reasons your fan may be defective, including electrical failure, faulty motor, or debris causing obstructions in the blades. 

When the fan is unable to provide air during hot weather or stoplight idling, the radiator may not properly disperse the coolant’s heat and could lead to dangerous temperatures. 

Cooling fan in front of radiator

Can I Drive an Overheating Vehicle

Short answer, no. 

Long answer, no. And that’s because driving with high temperatures in your engine can cause the metal block and internal components to warp, bend, or crack. Overheating can also eat through the crucial gaskets that prevent oil or coolant leakage within your engine. 

Ignoring this and continuing to drive will eventually lead to complete engine failure. Overheating can cause lasting damage to your engine within a minute of running, let alone an entire drive. 

Cooling System Services in Peoria

If you’re experiencing overheating and need a diagnosis, trust the expert technicians at Beachlers Vehicle Care & Repair in Peoria, IL. Our team has extensive experience servicing the cooling systems of all makes and models, and will return yours to working condition! Give us a call or schedule online today to meet with our friendly service advisors.