Question PC turns extremely laggy after 4 hours of usage

[Hereizer]

First of all I'll try my best writing in english as it is not my main language, thx for your understanding.

It has never done this before, but recently I had trouble switching on the PC so i decided to open the case (the backplate only, the one where we hide the cables) permanently so I can access the power cables easily if something goes wrong. It's more like a placebo I think bc some days the PC switches on at the first try and some days I have to push the Start switch tens of times until it finally turns on. idk if it is a power supply problem or something else.

Now, after 4 hours of just zapping in Youtube (or playing) it just turns extremely laggy and imposible to keep using the PC unles I let it "cool" until the next day. Performance in games has lowered significally too... Is it a temp problem? Shoud I just close the PC case? Shoud I change just the thermal paste? Shoud I change the power supply, watercooled fans or CPU?

 

[Hereizer]

The attached image shows the performance and temps with just a 1080p 60fps YT video. The PC is 9 YO and I always got great performance even in games until now.

 

[uWebb429]

@Hereizer

Your computer is overheating. The CPU heatsink and fan need to be cleaned and the thermal paste should also be replaced.

 

[Hereizer]

@Hereizer

Your computer is overheating. The CPU heatsink and fan need to be cleaned and the thermal paste should also be replaced.

I have just cleaned the cpu fan and changed the thermal paste... It still turns 100ºC (95ºC at 5% load) just after starting Windows... I have seen after cleaning the old thermal paste that the copper plate from the fan has a square (where it has contact with the CPU) different color from the rest of the copper plate... Could it be corrosion? It's just greyish copper with colorful rainbow like colors in the edges of the square...

I have cleaned tons of dust that I found inside the fan and now it just runs slower than before... could it be the thermal paste that I applied? It's weird because coretemp says 95ºC but the air from the fan is colder than the air in my room...

 

[uWebb429]

95ºC

The heatsink is not installed correctly. Does it use 4 push pins? You install those by pushing in 2 diagonal pins at a time. Do not push in one at a time. It is likely that or you did not clean it and apply enough thermal paste.

 

[silverz]

Definitely the heat. 95c on youtube is not normal. The air from the fan will be cold because all the heat is stuck there on your cpu by the sound of it.

Possibly mounting the cooler wrong... too much pressure on one side making it pop up away from the cpu on the other side or just not fastening it down properly.
If its one of those little round stock intel coolers they need more pressure than you might think to clip them down.
Also look on youtube how to apply paste as you might be doing what a lot of people do and using way too much.

Never heard of corrosion from paste before but after cleaning it the base of the cooler should be flat and smooth, no indents or anything.

 

[SkyNetRising]

I have just cleaned the cpu fan and changed the thermal paste... It still turns 100ºC (95ºC at 5% load)

What cpu cooler are you using?
Can you show a photo of your system with side panel removed?

 

[Hereizer]

The heatsink is not installed correctly. Does it use 4 push pins? You install those by pushing in 2 diagonal pins at a time. Do not push in one at a time. It is likely that or you did not clean it and apply enough thermal paste.

Definitely the heat. 95c on youtube is not normal. The air from the fan will be cold because all the heat is stuck there on your cpu by the sound of it.

Possibly mounting the cooler wrong... too much pressure on one side making it pop up away from the cpu on the other side or just not fastening it down properly.
If its one of those little round stock intel coolers they need more pressure than you might think to clip them down.
Also look on youtube how to apply paste as you might be doing what a lot of people do and using way too much.

Never heard of corrosion from paste before but after cleaning it the base of the cooler should be flat and smooth, no indents or anything.

What cpu cooler are you using?
Can you show a photo of your system with side panel removed?

Thanks you all... It was what I tought it could be after a lot of testing:
Fans were blowing cold air, the water tubes were both cold and cpu was 100ºC. So i tought that it could be the bomb inside the watercooling system not functioning and thus not letting the hot water flow through the system.
After this realisation, I bought the cheapest cpu cooler without watercooling, removed the fans from the old watercooling system and used them as system fans (behind the PC where all the usb connections are and the bottom) and now the PC is cooler and silent as ever has been (not before touching every fan control in the bios... I fear that these three times with the cpu at 100ºC could have done any damage to the cpu now... But for now It seems it's working.
Now look at the results with a 2k video 60fps (which was a bit hard even before the fault for my PC tbh):

 

[Hereizer]

Definitely the heat. 95c on youtube is not normal. The air from the fan will be cold because all the heat is stuck there on your cpu by the sound of it.

Possibly mounting the cooler wrong... too much pressure on one side making it pop up away from the cpu on the other side or just not fastening it down properly.
If its one of those little round stock intel coolers they need more pressure than you might think to clip them down.
Also look on youtube how to apply paste as you might be doing what a lot of people do and using way too much.

Never heard of corrosion from paste before but after cleaning it the base of the cooler should be flat and smooth, no indents or anything.

It was not that but after this repair I learned a lot and I never tought that simple thing as popping up bc of wrong pressure distribution could happen.. Thanks for the responses! The funniest thing about having these failures is the learning we get even if i break the PC (f.ex. I broke the wifi from my parents laptop after trying to clean and upgrade the cooling system but I learnt how were laptops built and which cables or pieces never to touch again).