CPU overheating: How to tell and fix

Purchases through our links may earn us a commission.

Excess heat is bad news for a computer. High temperatures can cause irreversible damage to electrical circuits and even fire or explosion.

It’s unfortunate that electrical circuits naturally produce heat in their operation. Due to the risk of irreparable damage by heat, virtually all computer cases are built to maximize airflow with spaces for multiple fans to pull in fresh, cold air and push out heat.

Over time and with regular use, your machine’s ability to draw heat from the CPU and push it away will become worse. Several things can affect the efficiency of a unit’s cooling systems, resulting in a build-up of heat and, ultimately, component damage.

This is why it’s important to know how to identify an overheating CPU, troubleshoot its causes, and take the necessary steps to prevent further overheating in the future.

Identifying the signs of an overheating CPU

An overheating CPU is no laughing matter. Continued use of a machine that is regularly overheating can and will lead to permanent damage to the components inside.

Once your CPU fries, it’s gone for good, meaning you’ll have to replace it outright.

Listen to the CPU fans

The first way of knowing if your CPU is overheating is by listening to the fans. Your CPU fan isn’t supposed to be running on full throttle all the time. 

Typically, CPU fans are set to run at different speeds. As your CPU heats up, its fans ramp up in speed to move hot air away from the CPU more quickly.

If you’ve noticed that the fans are unusually loud, even when you aren’t running an application that’s intense on the processor, that’s an early warning sign that your CPU might be getting too hot.

Reduced overall performance, even when doing simple tasks

Another telltale sign of an overheating CPU is when your computer struggles to perform tasks that it previously was fine with.

For example, if you notice your favorite game or video editing application seems to be loading more slowly or you’re dropping frames left and right, that could mean the CPU is doing what is known as throttling.

CPU throttling is when the processor becomes so hot that the system forces it to operate at a lower frequency to reduce the production of heat. The result is decreased overall processor performance.

You can check if your CPU is throttling on a Windows machine by going into the Task Manager (CTRL+Shift+Esc) and opening up the Performance tab. This will bring up a bunch of graphs and numbers but you’ll want to focus on the information about your CPU. 

Open up a CPU-intensive application, such as a photo editing application or video game, and watch how the Utilization and Speed numbers change over time. When the CPU is throttling due to overheating, utilization will often hit 100% and at some point, the CPU’s Speed will suddenly drop.

You’ll notice this happens several times over the next few minutes, causing several sharp peaks in the Utilization graph.

Random shutdowns and restarts

In cases of extreme overheating, modern CPUs are designed to shut off automatically. Usually, the minimum temperature the CPU must reach before it gets to the point of an automatic shutdown is quite high, often 90 degrees Celsius or more.

If your computer appears to shut down when you open certain applications, this might signify an issue with heat in your computer case.

If your computer ever gets to the point that it’s turning off on its own, you should immediately stop using the machine and start troubleshooting.

Every time your CPU reaches temperatures that high, the probability of it incurring permanent damage increases.

Check your CPU temperatures with third-party applications

If you want to look at the raw temperature numbers you can do that as well if you’re willing to install some third-party applications.

There is a ton of software options available that can provide you with temperature readings, from specialized temperature reading applications to proprietary software developed and published by CPU manufacturers.

Here, we’ll talk about one of the most popular third-party options that experts use for diagnosing CPU overheating issues.

Don’t worry, this is completely safe to use and won’t harm your system.

This software is called Core Temp and it provides you with a basic rundown of the make and model of your CPU, how many cores it has, how much power it’s consuming, and the average temperatures for each of its cores.

You can download the software from its website.

One quick note: don’t just blindly hit next as you’re installing. A list of checkboxes will pop up; be sure to uncheck all of the options except for the very top one, Install Core Temp, or you’ll end up installing some annoying extra software.

The important information is at the bottom under Temperature Readings. As you can see, my PC has 4 cores. The average temperature for each core is listed right beside the core number, followed by the minimum temperature, and load percentage.

Right above the average temperatures is the Tj. Max, or Temperature Junction Maximum, is the temperature limit where the CPU will begin to throttle (mine is 100 degrees Celsius).

When you’re browsing or the computer is idle, your average core temperatures should sit around 30-60 degrees Celsius.

When you’re performing a CPU-intensive task, such as photo editing or gaming, those temperatures can hit anywhere from 70-80 degrees Celsius.

You never want to see the temperatures hitting your CPU’s Tj. Max. If your system consistently hits the Tj. Max, that’s indicative of a heating issue and you should immediately start looking for what is causing the heat issue and possible solutions.

How to keep your CPU cool and prevent overheating

As we briefly touched on earlier, the basics of CPU cooling systems are quite simple. They pull heat from the CPU and expel them out of the case. We can break this process down into three simple steps:

  1. Draw heat from the CPU
  2. Push the heat out of the case
  3. Draw in cool, fresh air into the case

Your typical computer setup is cooled by a series of fans with different functions. Some fans pull in the cool ambient air around the case while others push hot air out of the case. 

Even complex liquid cooling systems operate on the same basic principle. A series of tubes push a constant stream of cool liquid across the CPU which pulls heat away from the component. The liquid which has been heated by the running CPU then passes through a radiator that then transfers this heat to the air outside of the case. The cooled liquid is then recycled back into the cooling system.

Let’s take a look at ways you can improve the efficiency of your cooling system at each of these stages.

Drawing heat from the CPU

Before we can talk about how cooling systems pull heat away from the CPU, it’s important to understand what thermal conductivity is. Thermal conductivity is how well a material can transfer heat and it’s measured in watts per meter Kelvin. Let’s compare the thermal conductivity of some materials commonly found in a PC:

  • The thermal conductivity of air is 0.0245 W/mK
  • Aluminum’s is 205 W/mK
  • Copper’s is 385 W/mK
  • Gold’s is 314 W/mK

A glance at the numbers shows that plain air is inefficient at transferring heat. Just placing a fan above the CPU is a terrible way to transfer heat away from the processor. For this reason, modern CPUs are also equipped with what is known as a heatsink.

A heatsink is a large, metal cuboid comprised of dozens of metal fins and its purpose is to dissipate heat from the CPU. Since heatsinks make direct contact with the metal surface of the CPU and are usually made of aluminum alloy or copper, they can transfer heat away from the processor far more quickly than air can.

Pushing the heat out of the case

Heatsinks are awesome at taking heat away from the CPU but they still dissipate it into the air inside the case.

Without a proper exhaust system, that heat will sit in the computer case, increasing the overall temperature of all the components within.

An exhaust fan is a case fan that’s installed to push this heat out of the case and into the ambient air.

You can’t just stick an outward-facing fan into the case and call it a day, though – placement is important.

Since heat rises, exhaust fans are generally installed higher up in the case and blow the heated air out of the top or back of the case.

That’s why if you’re going with a custom rig it’s best to check out and do some research into which is the best case to get. BTW you don’t have to sacrifice your peace for a good case with efficient cooling.

Drawing fresh, cool air into the case

In contrast with exhaust fans, intake fans pull in cool air from outside and blow it into the case.

You want to set up the placement of the fans to maximize airflow within the case.

This is done by placing exhaust and intake fans opposite of each other, allowing for cool air to blow over major, heat-producing components before it’s heated up and expelled through the exhaust.

Inspect your case for objects or dust that can obstruct air flow

Many cases of overheating CPUs can be traced back to dust build-up in the system.

Open up your computer case and take a good look at the components inside. If you haven’t cleaned out your computer in a long time, you’ll likely find layers of dust sticking to the internal components.

Inspect your fans as well; dust in the fans greatly affects the airflow in your case, making it difficult or impossible for the cooling systems to expel heat or take in new air.

Dust should be cleaned out using a can of compressed air.

Your first instinct might be to blow on the components to release the dust, but that’s not recommended. Blowing causes the dirt and dust to float up into the air where you can potentially breathe it into your lungs.

You also run the risk of accidentally blowing out droplets of saliva onto electrical components which can damage them or even cause a short. Additionally, your lungs might not even be capable of producing sufficient air pressure to dislodge the dust from the components.

Ideally, you’ll want to perform the cleaning process outside or on the floor. Turn off your computer and unplug it from any electrical sockets. Open up your computer case and clear out the dust with your compressed air using short bursts.

Replace the thermal paste

close-up Thermal compound on CPU chip in mainboard computer

As we learned, heatsinks draw heat from the CPU and dissipate it into the air inside the case.

Computer manufacturers improve the efficiency of this process even further by using what is known as thermal paste.

Thermal paste is a thick, paste-like substance that is made up of a special compound designed to have very high thermal conductivity. A small bit of paste is applied to the space where the CPU and heatsink make direct contact.

Thermal pastes allow for maximum heat transfer by ensuring there are no gaps between the heatsink and the CPU. If your system is overheating and at least a year old, after cleaning out the fans and internal components, you should consider reapplying the CPU’s thermal paste.

Unlock the latches that fasten the heatsink onto the CPU and carefully lift the heatsink to gain access to the CPU. You should see bits of thermal paste on both the CPU and the part of the heatsink that makes contact with the processor.

Use a cotton swab and some rubbing alcohol (ideally 90% or higher) and carefully remove the old thermal paste from both the CPU and heatsink. Let the alcohol dry for a bit, then apply the thermal paste.

One of the biggest mistakes new PC tinkerers make is applying too much or too little thermal paste on the CPU. Also if you have a syringe of thermal paste lying around make sure that it hasn’t expired.

You want just enough to sufficiently fill in the gaps between the heatsink and CPU, but not so much that the paste is spilling out the sides. The recommended way of applying thermal paste is by placing just a small, pea-sized dot of paste on the center of the CPU, then installing the heatsink.

In conclusion…

If your computer seems to be performing poorly, the fans are running on full throttle even when your PC is idle, or you get random shutdowns and blue screens, an overheating CPU could be the cause. 

If you’ve cleaned out the case and components and replaced the thermal paste and still find your system is running too hot, consider replacing the fans or adjusting their placement within the case to optimize airflow.

Purchases through our links may earn us a commission.