Is it necessary to re-apply the thermal paste every time you remove the CPU?

[Lumia925]

Hi,
I was having problems with my laptop, and I opened the whole thing up (following instructions on a youtube video).
I cleaned the dust and then put the whole thing back together, and the problem i was having (POST failure, could not be solved by reseating RAM) is resolved-the laptop is booting up fine and working fine. I have used it for a while, about 3-4 hours, and it's not heating up much, it's absolutely cold to touch (fan turns off) if I'm just browsing the internet. It heats up a little (fan starts rolling) if I play games, but not unusually hot, and there has been no thermal shutdown.
I didn't re-apply the thermal paste on the (heatsink/ top of CPU) while re-assembling. Is that step compulsory? Should I get some thermal paste (i don't have any at home), and open the whole computer again to re-apply it?
Thanks.

 

[ak47jar3d]

Generally yes. Every time you remove heatsink, you should clean old paste and reapply thermal paste.

 

[Wolfshadw]

Standard practice is anytime you remove the heat sink from the CPU, you clean both surfaces and re-apply thermal paste. When you remove and re-attach the heat sink without cleaning and re-applying thermal grease, you can introduce air pockets between the two surfaces which do not conduct heat away from the CPU. This, of course can cause damage to your CPU.

-Wolf sends

 

[Lumia925]

I emailed HP about the same time I started this thread, and got their reply today.
HP support wrote exactly what you've written above - there can be gaps between the contact surfaces which can result in the CPU overheating and shutting down, or reduce the life of the CPU even though there aren't apparent symptoms.
They suggested to stop using the computer immediately,
and not to power it back on "even for a minute"(<--quote from the email) until I'm done cleaning both the surfaces and reapplying fresh thermal paste.
I have stopped using that computer.
I'll get the thermal paste tomorrow. Thanks for the help both of you
Could you please suggest how should I proceed with the cleaning?
Should I use a piece of cloth dipped in water? I've never done this before..

 

[Wolfshadw]

Personally, I use cotton balls and Isopropyl alcohol (typically available at the corner drug store) to clean the processor and heat sink. Do not use water or any other liquid. At a minimum, use 70% pure alcohol.

-Wolf sends

 

[Lumia925]

Personally, I use cotton balls and Isopropyl alcohol (typically available at the corner drug store) to clean the processor and heat sink. Do not use water or any other liquid. At a minimum, use 70% pure alcohol.

-Wolf sends

Wolf I cleaned the old thermal paste using cotton balls dipped in Vodka
Applied the new paste, re-assembled the whole thing, and ran a stress test using THIS tool.
The test passes ("Very High Stress" mode)

I measured the CPU temperature while the test ran, and got this:

Read in THIS page the maximum operating temperature for this CPU is 85°C, and as you see above, my MAX temperature reached 80°C during the test-that's just 5°C less than the MAX allowed! Have I done something wrong? Did I mess up while applying the thermal paste? The vents were not blocked during the test. The fan is working good, It sped up and became pretty loud during the test, but within 30 seconds after the test completed, it slowed down and temperatures returned to 40°C-42°C range (I guess this means the fan is working?)
Why am I going so close to MAX? It's not OC'd, just put it to "High performance" power profile before the test, and nothing else..
PS: The CPU did not throttle down during the test, I kept CPU-Z running too, and it stayed constantly at 2095MHz, after the test completed, it varied from 798 to 2095 MHz, I switched to "Power Saver" power profile and only then CPU-Z rolled back to 798MHz and stayed constantly there.

 

[Wolfshadw]

Wolf I cleaned the old thermal paste using cotton balls dipped in Vodka

PLEASE tell me this is an April Fools Joke!

If it's not, shut down your system IMMEDIATELY and take it apart again! Go to the store and get isopropyl alcohol (AT LEAST 70% pure alcohol) and clean it again. Vodka is only 40% pure alcohol!

-Wolf sends

 

[Lumia925]

Damn, I keep messing this up... I'm not sure I can score that isopropyl thing without a prescription, but vodka is so freely available..
Ok, I'll see if I can get some of that in a drug store/ computer store...

 

[Wolfshadw]

Just look for rubbing alcohol. Any "drinkable" alcohol will leave a residue on your surfaces which does not conduct heat. This could then lead to damaging your CPU.

-Wolf sends

 

[Onus]

Isopropyl alcohol is not the same thing as "rubbing" alcohol, which may have other things in it (camphor?). I use the 91% stuff myself. It is commonly available in any drug store or pharmacy in the US ("chemist" in the UK). It is cheap, and no prescription is needed.

 

[Wolfshadw]

I just dug out my bottle from under the bathroom sink. It states: Isopropyl Rubbing Alcohol 91% by volume. That's what I've go, so that's what I go by. I'm sure I read somewhere that the minimum was 70% by volume.

-Wolf sends

 

[Onus]

The 70% stuff is common too, but imho has too much water in it.

 

[RealBeast]

In a pinch I don't see a problem with using 190 proof Everclear, makes my tongue numb anyway unless diluted with a mixer. :lol: