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Top Reasons Your Engine Overheats Even with Full Coolant

POR: Keith Benline
Close up of parts in engine head

It should go without saying that the engine of your vehicle is perhaps the most important piece of machinery under the hood. The power generated by the engine keeps your vehicle moving on the road, and should it grind to a halt, you will be going nowhere. Unfortunately, one of the most commonly seen issues with vehicle engines is overheating for a variety of reasons. This situation is only made more frustrating if you check under the hood and see that you aren’t low on coolant.

An overheating engine is quite dangerous as it can cause serious damage to internal components such as gaskets, cylinder heads, the engine block, and more, which can subsequently lead to a breakdown while driving. There are many reasons why your engine may be overheating even though you are fully stocked on coolant.

By learning the reasoning behind this, you can get your car diagnosed and fixed quicker so that you can get back out on the road.

Thermostat Malfunctions: The Hidden Culprit

The first potential culprit of an overheating engine not due to a lack of coolant is a malfunction with the thermostat. The thermostat is directly responsible for cooling down the engine by taking into account the current temperature and then either opening or closing the coolant valve. When an engine thermostat malfunctions, it may fail to detect an engine overheating and, therefore, not open the coolant valve to allow coolant to siphon heat from the engine.

Generally, the common signs that an engine thermometer is having issues include:

  • Erratic temperature changes on the engine temperature gauge
  • Strange sounds coming from the engine
  • Heating problems or a lack of heat coming out of the vents

Testing whether or not the engine thermostat is broken usually requires the assistance of a repair professional. The most common test is dropping the thermostat into boiling water of up to 200 degrees at a minimum and checking to see if the valve opens as it should. Naturally, this is a dangerous test, which is why it should be performed by a licensed professional.

Faulty Water Pump: The Heart of Your Cooling System

The second potential cause of an overheating engine is a faulty water pump. The water pump is an integral part of regulating the engine temperature as it moves coolant throughout the engine system. As the coolant passes by the engine, it takes heat away and cools off the engine. The coolant cannot move through the system by itself and is reliant on the water pump to help keep it moving using centrifugal force. The common signs that a water pump is failing include:

  • Coolant leaking underneath your vehicle or within the engine block
  • An inexplicable whining noise coming from the engine block
  • Steam or general overheating coming from the engine

Unlike the engineer thermometer, diagnosing a faulty water pump is slightly more possible for the average person, though it is still better to rely on a professional. First, you can inspect your water pump for signs of corrosion that may be affecting coolant flow or the engine operating temperature. If the water pump looks fine, then the next best step is to rely on a mechanic who can diagnose the issue by taking the water pump out and inspecting it.

Radiator Problems: Blockages, Leaks, and More

El third cause of an overheating engine tends to be a faulty radiator due to a variety of issues. For those unfamiliar with it, the radiator works as the key component of the heater core, which is the engine. After the coolant passes through the engine and absorbs much of the excess heat, it is carried to the radiator, where it runs against the radiator fans.

As this occurs, the heat is pulled from the antifreeze by cooling it via airflow brought in from outside the car. This cycle continues until the coolant is no longer hot, and then it is sent back through the system to absorb more heat.

There are many reasons that a radiator may not be working properly, but the most common are leaks, whether in the radiator cap or radiator itself or blockages in the passageways. Below are some of the common signs of a faulty radiator to keep an eye out for:

  • Discolored or sludgy coolant leaking out onto the ground
  • Coolant levels drastically fall due to a coolant leak
  • Thumping noises resulting from faulty radiator fins
  • Noticeable bubbles in coolant fluid

Air Pockets in the Cooling System: An Overlooked Cause

Moving beyond the traditional causes of issues in automotive cooling systems, air pockets are an often overlooked issue that affects engine temperature. This issue is typically most prominent after the draining and flushing of a vehicle’s radiator. During this process, air can sometimes get trapped within the new coolant, which then expands as the coolant begins to heat up. This bubble then moves to the coolant reservoir, but as the engine cools off, it pops and pulls the coolant back, which can lead to car overheating issues.

Luckily, air pockets in the cooling system are actually an issue that the average driver can solve themselves. To “bleed” your engine coolant, first start by turning off your vehicle and ensuring the engine is completely cold. Remove the radiator cap and top off the coolant via a funnel, then start the car’s engine with the cap still off and the funnel still in. This will ensure that as the coolant runs through the system, air can escape the funnel. Once you have run your engine for a few minutes, shut off the engine and top off the coolant system if the level has fluctuated.

Fan Failure: When the Cooling System Can’t Keep Up

The final common reason that the engine under the hood may be overheating is due to a cooling fan failure. Some vehicles, in addition to the radiator, also have one or more engine cooling fans that are either electrical or mechanical.

When a car overheats due to fan failure, it is most likely due to sensor issues or electrical issues that stop the fan from turning on, similar to when the thermometer fails to detect engine temperature. This fan is often built into the radiator, which means diagnosing an issue with it is relatively simple. Keep an eye out for some of the following signs:

  • You can see the fan not spinning even though your vehicle has been running for a while
  • The check engine light flicks on, especially when the vehicle has been running for an extended period of time
  • Your vehicle seems to overheat even at low or idle speeds
  • Visible damage to the radiator fan is apparent

Endurance Auto Protection Plans: Safeguarding Against Engine Issues

El worst thing a driver can experience is a sudden breakdown on the road, but the second worst thing is to find out that the repair cost is exceedingly high. Having an extended warranty, also known as an auto protection plan or vehicle service contract, can remove this concern by covering the costs of the repairs that must be performed on your car. As mentioned above, an engine overheating despite plenty of coolant means there could be an issue with a bad thermostat, water pump, radiator, cooling fan, and more.

Vehicle service contracts from Endurance Warranty, specifically the Superior and Supreme plans, offer coverage for the cooling system of your vehicle. The Superior plan offers coverage for the following:

  • Cooling fan (along with the fan motor and clutch)
  • Radiator
  • Heating core
  • Thermostat
  • Blowing motor
  • Hot water valve
  • Engine oil cooler
  • Cooler lines and fittings

The Supreme plan offered by Endurance, providing near bumper-to-bumper protection, covers every part of the cooling system except for any small part included on the exclusion list. Moving beyond the cooling system, both of the two plans above, as well as the option of customizable plans offered by Endurance, offer varying levels of coverage for the entire vehicle. This means you can create an extended car warranty or auto protection plan that suits your specific needs on the road.

Protect Your Engine with an Extended Warranty

No driver should be behind the wheel when their engine is overheating, as this can lead to serious issues on the road. In most cases, if there is coolant in the engine but your engine is overheating, you should simply take your vehicle to an accredited repair shop right away. Knowingly driving around with your engine overheating can potentially be dangerous, so don’t hesitate to visit a mechanic.

The costs associated with replacing parts that have failed in or around your engine block can be extremely high, but having an Plan de protección automática Endurance can take this concern away. By covering some, if not all, of the repair costs, you can breathe easier knowing you’ll be back on the road soon without burning a hole in your wallet.

Additionally, Endurance customers receive a suite of standard benefits like 24/7 roadside assistance, towing, rental car coverage, and trip interruption coverage. On top of that, you can activate our extra Beneficios de élite package for up to $1,000 in total loss protection, reimbursements for up to four tires per year due to road hazards, key fob replacement, and more.*

To learn more about how Endurance can help protect your vehicle, contact one of our accredited plan service advisors at (800) 253-8203 o request a FREE quote online. Alternatively, you can shop on our eStore to see your plan recommendations and pricing now.

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