When your temperature gauge is starting to go into the red zone, you might panic. But what exactly does it mean for your engine to be overheating?
There are many reasons that your engine could be overheating, and knowing these reasons allows you to pinpoint what might be causing the problem quickly and to try and prevent a minor inconvenience from turning into an expensive problem.
Common Causes of Engine Overheating
There could be several reasons for an engine to overheat, but if you are recognized with each of these, you may realize you can fix this problem yourself, or at least you will be able to give the details to your local service center and possibly save money on repairs.
#1. Low Coolant Level.
A relatively low coolant level in a vehicle’s cooling system will result in engine overheating. With no relative coolant flow, the engines’ ability to transfer increasing heat from the engine block to the vehicle’s radiator and hot water throughout the cooling system will appear to skyrocket and lead to catastrophic failures.
If this is the case, the source of the coolant leak must also be determined, as topping off the coolant is only a temporary fix.
#2. Stuck Thermostat.
A thermostat that remains stuck in the closed position can result in engine overheating. When the thermostat fails and gets stuck in the closed position, it effectively creates a blockage to the cooling system flow between the engine and the radiator itself.
It is possible that the conditions for overheating can exist in as little as 10 minutes during operation.
#3. Water Pump Failure.
A vehicle’s water pump circulates coolant throughout the cooling system. A failed water pump may be incapable of producing a sufficient coolant flow, which may quickly result in engine overheating.
In this case, replacement of the faulty water pump is required.
#4. Radiator Blockages.
Radiator restrictions could cause an engine to overheat. If there is one or more blockages within a vehicle’s radiator, the movement of coolant in the cooling system is affected.
In many instances, the worse the restriction is, the more extreme the overheating will be. One way to diagnose a radiator blockage is if there is a cold lower radiator hose.
#5. Inoperative Radiator Fan.
Almost all vehicles have the capability of using specialized cooling fans that allow for additional air to be forced across the radiator itself. The purpose of these fans is to help with the cooling process. In some applications, the cooling fans can be purely mechanical, while on other vehicles made in the last 15 years or so, the fans can be electric.
In either event, an inoperative cooling fan can quickly lead to engine overheating, especially if the vehicle is idling at a stoplight. Blown fuses could contribute to the failure of a fan as well.
#6. Faulty Radiator Cap.
Another potential source of engine overheating could be attributed to a failed radiator cap. The purpose of the radiator cap is to control coolant loss under pressure while maintaining a sufficient level of cooling system pressurization.
If a radiator cap failed, it would allow cooling system pressure to bleed off prematurely, and usually purge a bunch of coolant along with it.
#7. low Engine Oil Levels.
Excessive friction in an engine can quickly lead to a huge amount of heat build-up. If a vehicle is running low on engine oil, the increased friction caused by inadequate lubrication of moving parts will create tremendous increases in temperature that even the best cooling systems cannot overcome.
#8. Blown Head Gasket and/or Intake Gasket.
While this is usually at least somewhat rare in comparison to the greater number of other possible causes on this list, a blown head gasket and/or blown intake gasket could also cause an engine to overheat.
Depending on the failure, a blown head gasket or intake gasket can lead to the vehicle consuming coolant or in the event of a blown head gasket, the mixing of engine oil and coolant. While not a direct cause of cooling system efficiency, both of these scenarios are notable.
How to Locate the Source?
Identifying the source of engine overheating can often be a multi-step process, reliant on thorough diagnostics and attention to detail. The following steps can be used to assist in diagnosing these types of issues in an uncomplicated manner.
Always refer to a factory-specific service manual for your make and model of vehicle before you undertake repairs of an extensive nature.
Step 1 – Inspect Coolant Level
The first step is to check the vehicle’s coolant level and make sure it is filled to its maximum capacity. If it is below maximum capacity, top off the system with the proper type/grade of coolant.
You should also verify that the coolant is not contaminated in any way.
Step 2 – Locate Leaks (If Necessary)
If in the above inspection, it was revealed that your vehicle’s coolant level was below its normal operating capacity, the source of any leaks will have to be located. This may sometimes be done strictly using visual inspection.
If no leaks are found, a coolant system pressure tester can be used to simulate the lost pressure, and may help identify hard-to-locate leaks. Any leaks that are found should be repaired right away.
If a loss of system pressure is observed, yet no leaks are identified from the outside of the engine, further qualification of the engine’s head gasket(s) and intake gasket will be required.
Step 3 – Test Radiator Cap
Many coolant system pressure testers also have special attachments for testing radiator caps. It is prudent to perform a test of the radiator cap to ensure that it isn’t the root of the overheating problem.
During this test, the cap itself should spring open to the bypass position at the exact specified pressure. If this does not happen, replace.
Step 4 – Check Oil Levels
At this point, a quick check of the lube oil in the affected vehicle, oil should be topped off if not already.
Step 5 – Perform Operating Tests
Next, start the engine and allow it to run for several minutes to allow it to warm up to operating temperature. Looking at the vehicle’s operating temperature, lightly squeeze the vehicle’s top radiator hose, and feel both heat and pressure at this point.
If at this time you do not feel the heat and pressure, we can eliminate that as a possible overheating source and suspect a faulty thermostat.
Next, observe and then verify that the vehicle’s engine cooling fan does activate at its specified temperature. If not, further inspection of the fan and other components will be required.
Step 6 – Confirm Flow.
If all of the other above tests have been inconclusive, confirm that sufficient flow is taking place in the cooling system.
Using an infrared temperature gun/meter, check for hot spots or points of restriction taking place in the cooling system. And confirm that a significant temperature drop occurs through the radiator.