Thermal Paste Replacement: When MacBook, iMac, PC and Laptop Owners Really Need It (and When to Leave It Alone)

The verdict first: who should repaste and who should leave the case closed

Thermal paste is the thin layer between a processor and its heatsink. It does not cool anything by itself. It only fills microscopic gaps so heat can leave the chip. Over years it can dry out, crack or squeeze out, and the chip then runs hotter than it used to. That is real. But "replace the thermal paste" is also the most over-prescribed fix in computer repair, because the same symptoms (loud fans, slowdowns, heat) are far more often caused by dust, software, a failing fan or a dying battery. This guide gives you a way to decide before you touch a screwdriver.

The short version, by device type:

If you remember one rule: repaste only after you have proven that the cooling path is clean and that the temperature problem is hardware, not software. The next section is that proof, and it takes about fifteen minutes.

The 15-minute test to run before you buy paste

Most people who think they need thermal paste actually have one of five other problems. Work through these in order. Stop at the first one that explains your symptom.

1. Look at what the processor is doing at idle. A machine that sits at 60 to 100 percent CPU with nothing open is not a paste problem. On a Mac, open Activity Monitor, click the CPU tab and sort by "% CPU". On Windows, press Ctrl+Shift+Esc and sort the Processes tab by CPU. Browsers with dozens of tabs, a stuck update, a sync client re-indexing, a video call that never closed, or unwanted software mining in the background are the usual culprits. Our guide to fixing a MacBook that overheats covers the software side in detail.
2. Check the room and the surface. Apple states that Mac laptops are designed for ambient temperatures between 10 and 35 degrees C (50 to 95 degrees F), and that using the laptop on a soft surface such as a bed, couch or lap can make the fans run more. A laptop on a duvet in a 30 degree room will always run hot, whatever paste is inside.
3. Blow out the vents. Dust is the number one cause of real overheating. On a desktop, use short bursts of compressed air with the fans held still by a toothpick or pencil so they do not over-spin. On a laptop, you can often clear the exhaust vent with short bursts from outside, but the real clean needs the bottom cover off.
4. Listen to the fans. Grinding, rattling or a fan that never reaches full speed points to a failing fan. A fan that is silent while the machine is hot points to a fan, a cable or a sensor fault. None of these is fixed by paste.
5. Update and reset the basics. Install pending system and firmware updates. On a Windows laptop, check that the power plan is not stuck on a maximum performance mode that keeps the CPU boosted. On an Intel Mac, resetting the SMC can restore normal fan control after a sensor glitch (Apple documents the steps for each model on its support site).

If the machine is still hot at idle after a clean, with normal software load, and the temperature climbs quickly under load while the fans scream, then you are in paste territory. Now you need numbers.

Temperature thresholds that actually mean something

Forum posts quote very different "normal" temperatures because they mix different chips, coolers and workloads. The honest picture is that there is no single threshold, but there are useful bands, and two facts from the chip makers that change how you read them.

• Intel: Intel documents a "Tjunction max" for its processors, typically between 100 and 110 degrees C depending on the model. When cores approach it, the processor reduces power and frequency (throttling) on its own, and if that is not enough the system shuts down to protect itself. Touching the limit briefly under a heavy load is by design, not damage.
• AMD Ryzen 7000 and newer desktop chips: AMD describes a maximum operating temperature of 95 degrees C for the Ryzen 7000 series (lower on the X3D variants, which are reported at 89 degrees C), and the chips are designed to boost until they hit that limit under heavy multithreaded work. A Ryzen 7000 at 90 to 95 degrees under a render is normal. The same number on a ten-year-old Intel desktop at a light load is not.

So judge three things, not one: the idle temperature, the time to reach the limit under load, and how much performance you lose once there. The table below uses rules of thumb collected from vendor guidance and common repair practice. They are not warranty limits.

All figures are degrees Celsius and depend on the chip, the cooler and the room. Treat them as a screening tool, then confirm with a before-and-after comparison on your own machine.

How to measure it yourself (Mac and Windows)

On a Mac. macOS does not show a temperature in the menu bar, but Terminal can show thermal state. On Apple Silicon and recent macOS versions, run sudo powermetrics --samplers thermal -n 1 and read the "Current pressure level" line: Nominal is normal, and higher levels (Moderate, Heavy, Trapping, Sleeping) mean the system is already throttling to cool itself. On Intel Macs, sudo powermetrics --samplers smc -n 1 typically reports CPU die temperature and fan speed. The exact output differs between macOS releases, so treat the field names as a guide. Third-party sensor apps also work, but install only well-known, signed ones from a source you trust, because a fake "Mac cleaner" is a common scam.

On Windows. Task Manager shows CPU load and clock speed on the Performance tab. For temperatures use a free monitor such as HWiNFO or the vendor's own utility. Record three numbers: idle, after five minutes of a stress test, and the clock speed at the end of that test.

The stress test. Run a CPU stress tool for five minutes with the machine on a hard surface and the fans on automatic. Write down: the temperature at 30 seconds, at 5 minutes, and the CPU frequency at the start and at the end. Keep a note card. After any fix (cleaning, repaste, new fan) you repeat the same test. The only honest proof that a repaste worked is a lower temperature and a steadier clock speed in the same room under the same test.

Safety. Stop the test if you smell burning plastic, the case becomes too hot to touch, or the system shuts off. A shutdown during a stress test is the safety system doing its job, but it is also a sign to stop and diagnose rather than repeat it.

Symptom to cause table: is it really the paste?

Notice the pattern: paste problems build slowly over years. A sudden change is almost never the paste. If your machine got hot overnight, look for a fan failure or a software change first, and see our guide to a slow laptop for the general diagnostic path.

Paste types compared: what to buy and what to avoid

Not all compounds are interchangeable. The wrong choice does not just perform badly, it can short a board or corrode a heatsink. Here is how the main families compare.

For almost everyone, the right answer is a quality non-conductive paste in a small syringe. You get a safe margin for error, and the difference between a mid-range and an expensive non-conductive paste is usually a few degrees, not a transformation. Spend more on the right cleaning solvent and the right tools than on exotic paste.

About liquid metal. It lowers temperatures on some platforms and is used by some manufacturers in sealed designs, but it is gallium-based, and gallium reacts with aluminum. Many laptop and Mac heatsinks use aluminum parts, and a bead that migrates can bridge tiny contacts next to the chip. If you are asking whether you should use it in a MacBook, the answer is no. Leave it to people who bake the risk into their hobby on a desktop with a nickel-plated or bare copper cooler, and who accept the chance of a dead board.

What is the paste in your machine now? You usually cannot know without opening it, and manufacturers do not publish the product. What you can know is that factory paste is applied by machine in a precise pattern and is chosen to bridge the gaps of that specific design. A different paste may or may not beat it in the first year, but it can beat a dried-out one after year five.

Apple Silicon versus Intel Macs: very different answers

This is where most online advice is outdated, because it was written when every MacBook had an Intel processor that ran very hot. The situation today splits in two.

Intel Macs (2012 to about 2020)

Thin Intel MacBook Air and MacBook Pro models were known to run hot, especially the 2016 to 2019 generation, where the processors were pushed hard inside slim cooling systems. After four to six years, dried paste plus dust can turn those machines into space heaters with fans that never rest. On this group, repasting plus a proper dust clean is a legitimate, often effective repair. Many owners report clearly lower temperatures and quieter fans afterwards, and the improvement is largest on machines that were already throttling.

It is still a skilled job: you work around a lithium-ion battery that is often glued down, the trackpad cable, the display hinge and screws that are tiny and sometimes pentalobe. If the battery is swollen, stop. A swollen battery can burst and must be handled by a professional who knows how to remove and dispose of it.

Apple Silicon Macs (M1 and later)

Apple Silicon changed the thermal picture in three ways, and the first two are the reason repasting is rarely worth it:

1. Far less heat for the same work. These chips deliver high performance at much lower power than the old Intel parts, so a MacBook Air with no fan at all can handle normal use. There is simply less heat to move.
2. Thermal design is matched to the chip. The cooling system is designed around the chip's actual power, and the machine manages heat by adjusting performance well before components are in danger.
3. The compound and the chip package are less forgiving to disturb. The processor is not a socketed chip with a flat metal lid you can wipe and reapply. Opening the heatsink on one of these machines means working on a delicate package, and a slip can cost you a logic board that is expensive to replace. Apple's own service model leans on whole-part replacement rather than board-level work, and independent technicians generally avoid repasting these machines unless there is clear evidence of a fault.

Honest caveat: the Apple Silicon generation is only a few years old, so there is no long-term data on how its compound ages beyond five or six years, and we do not claim to know. What we can say is that for an M-series Mac in its first years, if it runs hot, the cause is nearly always software, a blocked vent, a failing fan on models that have one, an unsuitable surface or a battery problem, not dried paste. The sensible approach is to diagnose those first and only consider paste if a skilled technician finds a specific reason.

iMac: why the glued screen decides everything

An iMac is a desktop in name only. The internals sit behind the display, and on most models from about 2012 to 2020 the front glass is held in with adhesive strips. To reach the CPU heatsink you cut those strips, lift the glass and panel, disconnect several fragile cables, and later replace the adhesive. Done well, it takes an hour or two. Done badly, you scratch the panel, tear the backlight cable or leave dust trapped behind the glass for good.

The classic iMac heat issue is a combination: a hard drive sitting in a warm enclosure, a fan profile that ramps up because the drive's temperature sensor reads high, dust build-up around the vents and, on older models, aged paste on the CPU and GPU. If your iMac fan is loud, the more probable story is dust and the drive. Replacing the old spinning drive with an SSD often cuts heat and noise on its own. See our SSD versus HDD upgrade guide for the cost trade-offs.

Verdict: leave iMac repasting to a technician with the proper adhesive strips and the right glass-lifting tools. If you are confident, at least stop before cutting anything and confirm the plan with the model's service documentation. Newer Apple Silicon iMacs are thin, glued designs where we see no good reason to attempt this at home.

Safe DIY on a desktop PC: step by step

A desktop tower is the best place to learn this job. You can see everything, parts are standard and a mistake is usually cheap to fix. Allow 45 to 90 minutes the first time.

What you need

• A tube or syringe of non-conductive thermal paste (a small amount is enough for several applications)
• 99 percent isopropyl alcohol, or at least 90 percent, and lint-free cloths or coffee filters
• A small Phillips screwdriver set, a plastic card or spreader if you want to spread paste
• A good light, a clean surface, and a few small containers or a magnetic tray for screws
• A static strap, or the habit of touching bare metal on the case before touching parts

The procedure

1. Shut down, unplug and discharge. Power off, switch off the power supply, unplug the cable and press the power button for a few seconds to drain the residual charge.
2. Photograph everything before disconnecting. Take pictures of the fan connectors, the cooler orientation and the screw order.
3. Remove the cooler. Unplug the cooler's fan cable. For a stock Intel cooler with push-pins, rotate each pin a quarter turn as shown on the cooler, then lift each corner in turn. For a tower cooler with a bracket, loosen the screws in a cross pattern, a little at a time. If the cooler seems glued to the chip, twist it gently by a few degrees to break the paste's seal rather than pulling straight up. On some platforms, pulling a stuck cooler can lift the chip out of the socket with it, which can bend pins. A short warm-up first (run the machine for five minutes, then power off and unplug) can soften old paste and help it release.
4. Clean both surfaces. Wipe the old paste off the chip's metal lid and off the cooler's base with alcohol and a lint-free cloth. Work gently, always wipe away from the socket and from the surrounding components. Let the alcohol evaporate fully, about a minute.
5. Apply new paste. A pea-sized dot (about 4 to 5 mm, a bit smaller than a grain of rice for a small chip) in the center is the standard method on a square lid. For very large chips, an X or a few small dots can give better coverage. Do not spread it with your finger. The cooler's pressure will spread it.
6. Remove the plastic film. New coolers often have a clear film on the base. Peel it off. Forgetting it is one of the most common mistakes and causes immediate overheating.
7. Refit the cooler straight down. Lower it without sliding. Tighten the screws or pins in a diagonal sequence, a little at a time, so pressure is even. Do not overtighten: finger-snug plus a little is enough.
8. Reconnect the fan, close the case and boot. Check in the BIOS or monitoring tool that the fan is spinning and the temperature at idle is sensible.
9. Retest. Repeat the five-minute stress test from earlier and compare it with your before numbers.

A realistic outcome: on a desktop with truly dried paste and a dusty cooler, a 5 to 15 degree drop at load is common, and on machines that had a mounting error, the drop can be much larger. If the numbers barely change, the paste was never the problem and your issue lies elsewhere (airflow, fans, the cooler itself, or the chip's own power settings).

Windows laptops: when DIY is realistic

A Windows laptop sits between a tower and a MacBook. Some are easy: a bottom panel held by ten screws, a visible fan, a heatsink with numbered screws. Others are glued, hide screws under feet and stickers, or place the heatsink under the board. Before starting, search for your exact model's service manual (the manufacturer often publishes one) and decide from that.

• Disconnect the battery first. There is usually a small connector on the mainboard. Do this before touching anything else.
• Loosen heatsink screws in the numbered order, reverse to tighten. Laptop heatsinks often have 1, 2, 3, 4 stamped beside the screws.
• Check the thermal pads. Many laptops have pads on memory chips, VRM or the GPU. Do not discard them casually. Reuse them if they are intact and still springy, replace them with the same thickness if torn. A pad of the wrong thickness leaves a gap or crushes components.
• Use a very small amount of paste. In a laptop, a small dot or a thin line is enough. Too much squeezes out near fragile components.
• Clean the fan blades and fins while you are in there. In many laptops this alone gives you most of the benefit.

Honestly assess your own skill. If you have never opened a laptop, a heatsink job is a poor first project. A cheaper practice run is replacing the keyboard or an SSD on a spare machine. If a pro opens it for you, most of the cost is labour, not parts (see the cost section below). For the cost comparison between brands, our Mac versus PC repair cost guide gives ranges.

When not to open a MacBook, in plain words

Do not open it yourself if any of these is true:

• It is an Apple Silicon model and runs normally (even if warm) in a cool room.
• The battery is swollen, the trackpad is lifted or the lid does not close flat.
• It has ever had liquid damage. Heat can be a symptom of corroded sensors, not paste. See our guide in French on what to do after a spill for the emergency steps, then get it checked.
• You do not have a proper pentalobe and Torx driver set, plus plastic opening tools.
• The machine holds data that is not backed up. Back up first, always, and test the backup. Our explanation of data recovery versus backup shows why.
• It is under warranty or covered by AppleCare. Opening it yourself can complicate a claim. Check Apple's terms for your model before opening anything.

If it is an Intel MacBook out of warranty with real thermal throttling, a clean and a repaste by an experienced technician is a fair job. Ask them three questions: Will you photograph the old paste and the dust? Which paste are you using, and is it non-conductive? Will you show me the before and after temperatures? A good technician says yes to all three.

The ten mistakes that ruin a repaste

1. Too much paste. It squeezes out, and on a laptop can reach contacts. It does not cool better, it insulates.
2. Too little paste or an unevenly seated cooler. Leaves hot spots and some cores much hotter.
3. Forgetting the cooler's protective film. The machine overheats in seconds.
4. Using conductive liquid metal on the wrong design. One bead on the wrong spot kills a board.
5. Using tissue or paper towels. They leave fibres that collect heat and dirt. Use lint-free cloths.
6. Touching the contacts on the underside of a socketed chip with your fingers.
7. Overtightening heatsink screws. A cracked chip or bowed board can follow.
8. Skipping the dust clean. You can repaste and still have a clogged fin stack.
9. Mixing up screws. Laptop screws vary in length. The wrong one can crack the board.
10. Not testing before and after. Without numbers you cannot tell if the job worked.

Myths worth dropping

• "New paste every year." Quality paste on a well-mounted cooler lasts years. Annual repasting adds risk, not benefit.
• "Hot means broken." Modern chips are designed to run near their limit under load (AMD says so for Ryzen 7000; Intel documents throttling as a normal safety mechanism).
• "More expensive paste fixes a hot laptop." A dust-blocked cooler beats any paste.
• "Paste fixes a slow Mac." Most slow Macs are slow because of storage, memory pressure or software. Our buyer's guide and the slow-laptop guide above cover that.
• "A hot case means paste failure." The case is hot because the heatsink is moving heat to it. That is cooling working.

What it costs in Canada: DIY versus paying a technician

Prices vary by shop and city, so treat these as typical ranges in Canadian dollars to budget with, not quotes. IT Cares does not sell parts or do board-level repair; for hands-on work we guide you remotely or refer you to a trusted local technician.

The cost trap: paying a shop 150 dollars to repaste a machine that was actually slowed by software, a full drive or a worn battery. A 60-minute remote check before the repair can save that. The reverse trap is also common: spending months nursing a ten-year-old laptop that would be cheaper to replace. As a rule of thumb, if a repair quote exceeds about half the price of a comparable new or good refurbished machine, think carefully about replacing instead. Our guide on laptop versus desktop repair costs helps with that decision.

Three realistic scenarios

Realistic scenario (illustrative, not a real client): a 2018 Intel MacBook Pro. A freelancer's 15-inch laptop works well for email and then slows to a crawl in video calls, with fans at full speed. Idle is already 58 degrees C. A thorough dust clean drops idle to 46 degrees, but the call still throttles after about two minutes. A technician finds dry, cracked compound and replaces it. The same video call now holds 80 to 85 degrees and stays smooth. Cost: roughly 160 dollars at a shop. Lesson: the dust clean fixed half the problem, paste fixed the rest, and the numbers proved it.

Realistic scenario (illustrative): an M2 MacBook Air that "feels hot". The owner suspects the paste after two years because the aluminum body is warm during a Zoom call. Activity Monitor shows a browser tab and a sync client using 70 percent of the CPU. After closing them and moving the laptop from a duvet to a desk, the thermal pressure reading stays at Nominal and the case cools. Cost: 0 dollars. Lesson: a warm case under a normal workload is the cooling system working, and opening an Apple Silicon Mac was never the right move.

Realistic scenario (illustrative): a five-year-old gaming desktop. A home PC that ran 72 degrees C in games now reaches 94 degrees within two minutes and the frame rate drops. Dust has packed the tower cooler fins, and a corner screw is slightly loose. The owner blows out the dust, reseats the cooler with fresh non-conductive paste and checks the film is removed. The new test shows 76 degrees. Cost: about 15 dollars of paste and alcohol and one evening. Lesson: on a desktop, a dust clean and a proper remount deliver most of the improvement, and it is the safest place to learn.

Checklist: before, during and after a repaste

When to call a pro

Call a professional, or ask us for a remote check first, if any of the following applies:

• The Mac or laptop shuts down on its own under load, and a clean did not help.
• You smell burning, see a bulging case, or the battery is swollen.
• It is an Apple Silicon Mac that runs hot with nothing running. That points to a hardware fault, not routine paste ageing.
• It is an iMac, or a thin laptop with glued parts.
• You cannot afford to lose the data on it.
• You are not sure whether the problem is heat at all.

IT Cares has provided remote and on-site IT support in Quebec and across Canada since 2014. A remote session can separate software heat from hardware heat in about an hour: we look at what is running, power and thermal settings, storage health and the sensor data, then tell you honestly whether to repaste, replace a fan, protect your data or replace the machine. If hands are needed, we point you to a trustworthy technician near you. We do not push unnecessary repairs.

Official resources

• Apple Support: Keep your Mac laptop within acceptable operating temperatures
• Apple Support: About fans and fan noise in your Apple product
• Intel: Information about temperature for Intel processors
• AMD: Ryzen 7 7700 product page (specifications)

Frequently asked questions

Related guides

• MacBook overheating: how to fix it
• Laptop running slow: causes and fixes
• Intel Mac vs Apple Silicon: worth buying in 2026?
• Mac repair vs PC repair cost comparison
• Laptop vs desktop repair cost guide
• SSD vs HDD upgrade and repair cost guide
• Data recovery vs data backup: the difference
• Mac won't wake from sleep: fix

Sources and official references

Last verified: October 4, 2026

• Apple Support: Keep your Mac laptop within acceptable operating temperatures (search result, opened 2026-10-04)
• Apple Support: About fans and fan noise in your Apple product
• Intel: Information about Temperature for Intel Processors (opened 2026-10-04)
• AMD: Ryzen 7 7700 product page