Engine Temp Spikes Then Returns to Normal – Reasons and Fixes

A car engine generates a lot of heat during its normal operation. It's normal behavior for your engine to get very hot while it's running. But it is also possible for it to generate too much heat and get damaged. Automotive engineers build their cars with several safety features that keep your engine in a safe temperature range. One of the most important is your temperature gauge. 

Engine overheating highlights

• Level of urgency:very high
• Commonreasons:low coolant, thermostat problems, coolant blockage, radiator fan problem
• DIY diagnostics:possible but complicated
• DIY repair:impossible
• Price of repair:$300 - $650
• Time for repair:3 - 6 hours
• If ignored:engine failure, low performance, cooling equipment damage

Reasons for Engine Temperature Spikes

Monitoring and regulating the temperature in your car requires several sensors and systems working in concert. If one of these parts fails or behaves irregularly, the whole system is affected negatively. This can cause incorrect or erratic temperature readings and overheating. 

• Thermostat Failure

The thermostat is a part of the cooling system that regulates the flow of coolant. The thermostat opens when the engine is too hot, allowing coolant to flow to the radiator and cool down the engine. When the engine gets cold the thermostat closes to restrict the flow of coolant to the radiator, allowing the engine to warm itself up.

The thermostat is crucial to temperature regulation. When it fails the engine is prone to damage from overheating. Thermostat failure is usually a result of the thermostat getting stuck in either the closed or open position. 

• Low Coolant  

The coolant in your car is an important part of its cooling system. Although the coolant is contained in a closed system, some problems can cause your coolant level to drop over time. When the coolant reaches a low level, your car won't be able to effectively eliminate excess heat. This results in overheating and erratic movement of the temperature gauge. 

• Faulty Radiator Fan

Your radiator fan is one of the most critical parts of the car's cooling system. It pulls cold air in to cool the coolant or water in the radiator. The radiator fan is particularly useful when the car is idling or moving too slowly to cool the engine with moving air through the grille.

A faulty fan might behave erratically, starting and stopping at random. If your car is moving slowly or idling, you're likely to notice this as the engine temperature rises and drops quickly.

If you've noticed that this issue appears mainly when you're idling or moving at low speeds, then your radiator fan probably needs to be replaced.

How Can You Fix Engine Temperature Spikes?

Once you notice your engine temperature spiking, you need to act fast to identify and fix the cause. It indicates an issue with your cooling system. If your cooling system has failed completely, you might find your car overheating in a matter of minutes. Overheating can have catastrophic results on your engine, resulting in expensive repairs or even a full engine replacement.

You'll find below a list of causes for engine temperature spikes, as well as your options on how to resolve the issue before your engine overheats.

1) Replace the Thermostat

If you're dealing with a faulty thermostat, then you'll need to replace it with a new one. It is not worth attempting to repair the faulty thermostat, because it is likely to fail again shortly. You can find a replacement online or at your local repair shop. As car parts go, they are generally inexpensive.

You can have the thermostat replaced by a mechanic, but you can fix it yourself with the right tools and knowledge. If you are technically inclined, follow these steps to replace it yourself.

• Make sure the engine is off and completely cool.
• Locate the thermostat housing. This is the metal housing where the radiator hose meets the engine. Place a pan beneath it to catch the coolant that will pour out, then remove the bolts with a wrench.
• Remove the thermostat from the housing.
• Install the new thermostat into the housing on the engine. Make sure the short end of the thermostat faces the pipe, while the long end goes into the housing on the engine. This is important to note because it is possible to install the thermostat backward, but it will not work as intended.
• Attach the housing cover and tighten the bolts with your wrench.
• Pour the coolant back into the radiator.

2) Top Up the Coolant and Locate Any Leaks

When the coolant in your car has fallen to low levels, you may be dealing with a coolant leak. While you can simply fill the radiator back up with coolant, this is a temporary solution. If you don't find and seal the leak, it is only a matter of time before you end up with a low coolant level again, wasting time and money.

Before you can begin sealing the leak, you will need to locate the cause of the problem. The most common trouble spots for radiator leaks are the hose clamps, radiator hose, and radiator.

You'll need to visually examine these parts for any traces of green coolant liquid pooling or bubbling where it's not supposed to be. Some things to look out for are:

• Rusted or slacking metal hose clamps

The hose clamps are metal rings that close tight onto the hoses to secure them to other parts of the cooling system. They can weaken or break because of rust or age. If you find a leak from a bad hose clamp, you will need to remove it and replace it with a new one.

• Damaged or cracked radiator hoses

The hoses that deliver the coolant to the engine and back are made of rubber. The extreme conditions under the hood can cause this rubber to degrade and develop small cracks where the coolant can leak through. 

Make sure to examine the bends and corners of the hose. These spots are most likely to wear down first. Once you have located a leaking hose, you will need to replace it.

• A cracked, dented, or leaking radiator

Radiator leaks are much more likely when you drive rough roads. This is because debris or rocks kicked up by tires can damage the radiator on impact. 

Look out for drops of green fluid beneath the very front of the car. You can also check between the radiator grille for traces of coolant.

If you find evidence of a leaking radiator, you will need to replace it. This can be done on your own, but it might be easier to get a mechanic to do it.

Once you've identified and fixed the cause of your leak, you can top up your coolant.

3) Replace the Faulty Radiator Fan

If you have a faulty radiator fan, you'll need to replace it. Before you go online to search for a suitable replacement fan, you'll need to confirm that your fan is indeed bad. All you need to do is lift the hood of your car and let the engine idle. Observe the motion of the radiator fan. If it rotates fast and steadily, then it is fine. If its movement is sluggish or irregular, then it is faulty and needs to be replaced urgently. 

You can find a replacement fan for your vehicle online. You can have a mechanic install it for you, but the process takes 20-30 minutes if you have the right tools and a DIY attitude.

• Let the engine cool down.
• Disconnect the battery from the car.
• Remove any bolts that are holding in the fan assembly. Depending on your car, you may need to remove other hoses or wiring before you can remove the fan from the car.
• Locate and unplug the power connector for the fan.
• Remove the fan assembly from the vehicle.
• Locate the bolts holding the fan into the assembly and remove them.
• Remove the faulty fan from the assembly and install the replacement fan in its place.
• Return and bolt the assembly into the car. Attach any hoses or wiring you removed before.
• Connect the battery back to the car.

Conclusion

Cars come with cooling systems to protect them from the high levels of heat they produce while they run. But it is still important to make sure that your engine doesn't overheat to avoid permanently damaging or destroying it. You can stay aware of your engine temperature by looking at the temperature gauge. When the gauge begins spiking and suddenly drops, then something is going wrong with the cooling system. 

By diagnosing the problem, you can determine whether the cause originates from your coolant level, thermostat, or radiator fan. Once you've identified the origin of the problem, you can choose the appropriate method of fixing it. This way you can have a reliable temperature gauge and keep your engine safe from overheating.