5-minute checks
Can you see kernel_task at the top of the list? This process is not the culprit: macOS uses it to occupy the processor and slow it down when it gets too hot. It drops back on its own once the temperature falls. So the real question is why the processor is overheating.
During use or from start-up?
- During use: if the fan gradually speeds up, even for light tasks, your Mac is not dissipating heat properly. Dust, dried-out thermal paste or a tired fan are the likely causes.
- From start-up: if the fan runs at full speed before you even reach the desktop, your Mac is no longer receiving information it needs to control it, so it runs it at maximum speed. The cause is almost always hardware.
- With a Mac that no longer charges: if the fan is running at full speed and your Mac won’t charge, it is a different fault. See our article MacBook not charging.
Hardware causes
- Dust: it clogs the fan and the heatsink fins. This is common on a Mac that is several years old.
- Dried-out thermal paste: the paste between the processor and the heatsink has dried, so heat transfers less efficiently to the heatsink.
- Worn fan: it rubs, whines or vibrates, and no longer cools your Mac sufficiently.
- Liquid damage: this is often the cause of a fan running at full speed from start-up. In the Macs we repair, the top case keyboard, the trackpad or its flex cable are often affected, and sometimes the logic board itself. See our article what to do after liquid damage.
Repair: which part to replace
We recommend working in this order, as each step costs more than the last:
- Cleaning: open your Mac, disconnect the battery and remove the dust from the fan and heatsink, dry and without any liquid. Our MacBook cleaning kit contains everything you need.
- Thermal paste: remove the old paste from the processor and apply fresh paste before refitting the heatsink. You can use our MacBook thermal paste (3 g syringe).
- Fan replacement: if it is noisy or not spinning properly, it needs replacing. The fan varies by model: you can easily find the right fan for your model.
- Heatsink: if it is damaged or poorly secured, it can be replaced. Here are all the heatsinks available.
- After liquid damage: if the fan runs at full speed from start-up, open your Mac and look for signs of corrosion on the flex cables. Then replace the affected parts one at a time: the top case keyboard, the trackpad or the trackpad flex cable. If the problem persists, you will need to replace the MacBook logic board.
Find the part for my Mac
Not sure of your model? Quickly identify the parts you need for this repair without making a mistake.
Need help with the repair? We offer tutorials to guide you step by step through replacing the part. Our team of technicians is also on hand if you need advice.
