Heat is the quiet cause behind a lot of complaints that get blamed on software: slowdowns after twenty minutes, sudden shutdowns under load, a fan that sounds like a hair dryer, and a mouse that stutters. The fix is nearly always physical.
Step 1 — Confirm it is heat
Install a monitoring tool that shows package temperature, or read it from BIOS. Under load, a healthy CPU sits in the 60–80°C range. Above 90°C it is throttling; above 95–100°C it will shut down to protect itself.
If the slowdown arrives only after a while and clears after a rest, that is thermal throttling, not a slow machine.
Step 2 — Dust, the cause of most of it
- Power off and unplug. On a laptop, remove the battery if you can.
- Blow air through the exhaust side first, then the intake, so you push dust out rather than deeper in. Hold fans still with a finger or a cable tie — spinning them with compressed air can damage the bearing.
- Desktops: the front intake filter is usually a removable panel. Rinse and dry it fully before refitting.
- Laptops: if the vents are packed solid, the bottom panel usually comes off with a handful of screws and the heatsink fins can be cleared properly. Go slowly and keep the screws in order.
Step 3 — Airflow and placement
- A laptop on a duvet, cushion or lap blocks its intake completely. Hard, flat surface, or a stand.
- A desktop with the rear pressed against a wall recirculates its own hot air. Leave 10 cm of clearance.
- Cable runs across the front intake defeat the whole case design. Tie them back.
- If the machine draws air in through a filtered front and exhausts at the rear, keep that direction — reversing one fan creates a pocket of hot air that no fan can clear.
Step 4 — Thermal paste
Paste dries out after five to seven years and stops transferring heat. If cleaning did not fix the temperatures, and the cooler has been on for years, reseating with fresh paste is the next step. A pea-sized amount in the centre, cooler pressed down evenly, screws in a diagonal pattern.
Do not do this on a laptop unless you are confident — heatsink screws are often numbered and must come out in sequence.
Step 5 — Fan noise without heat
If temperatures are fine but the fan is loud, the fan curve is the problem, not the cooling. Most motherboards and laptops allow a quieter profile in BIOS or the manufacturer's utility. A fan also rattles when a bearing is going, and that is a $10 replacement rather than a fault to investigate.
When it is a hardware fault
A machine that shuts down within minutes even when cool, with a new fan and clean vents, may have a failing pump on a liquid cooler or a heatsink that has come loose. Both are cheap parts and worth replacing — but check the cheap things first.