XPS 15 9560 Phillips screws won't budge

Would it be too risky to try using WD-40?

We would not use WD-40.

Update August 6 = Hi. I did that, they were able to open it and cleaned the whole inside, while also reapplying thermal paste to the CPU and GPU. I tried it now and the temperature has improved a bit, not going over 50ºC. The fans are still on pretty loud basically all the time. What could it be? Maybe drivers or firmware?
manut99

Is the Dell Power Manager Service Thermal Management set to Ultra Performance? If yes, change it to Optimized, retest. Then Cool, retest. Then Quiet, retest.

I had downloaded this before opening the computer. I have tried all modes now and Quiet still has fans turned on, even though it's the most quiet setting. Also, I feel like the CPU should be at lower temperatures than 40-50 when idle.

When I turn it on it's dead silent. After a couple of minutes the fans turn on but pretty unnoticeable. Then some more minutes go by and the fans ramp up to very noticeable and annoying speeds.

Can you see how the system's fans perform outside of Windows, like if you enter diags again and let it sit there, or in the BIOS? This might not change it but I was curious. Also, can you right click on Start, open Task Manager and check if there is anything using the processor when it is at idle? You might want to sort that field for Processor use (highest to lowest) just to see if something is causing a spike/using resources. 

Great suggestions, thanks. I'll try the BIOS one in a while, but I did the one with task manager and everything seems normal: 

1) I'll have to try the BIOS/Clean boot tomorrow.

2) If by flat surface you mean to ask if there's anything that can be blocking the air intake, the answer is no. In fact, 90% of the time I rest my laptop on something like this so it can get more air.

3) Yes, there was definitely an audible difference when switching between modes in the Dell Power Manager.

4) This is an observation that happened just a few minutes ago. I had turned my computer on from sleep and was just watching some videos on YouTube. The first minutes were completely silent, and after that there was minimal fan noise throughout. The time came to plug into AC and just seconds later the fans came on pretty loud. I just think that may give us a clue as to what the problem is (if there is any problem. My computer is like three and a half years old, maybe it's just got to do with wear and tear.). Just in case you ask, I had the "Power mode" set to best battery life when charging.

Lastly I just want to thank you guys, especially Brad, for putting time and dedication into helping people, I really appreciate it.

First, closely examine PDF Service Manual and be sure those are the proper screws to remove.

There is likely just a bit too much (temporary) thread-locker on them.

Whatever you do ... do not strip-them-out. I doubt they are Phillips head anyway. More likely to be JIS , so be sure to use the proper screw-driver type and size.

https://chapmanmfg.com/blogs/news/phillips-bits-vs-jis-bits-whats-the-difference

- Left it in the BIOS for a while, plugged into AC, and the fan was on but with minimal noise. Later I went into regular windows and the fans ramped up.
- Did the clean boot, same routine as before: Dead silent. After a couple of minutes the fans turn on but pretty unnoticeable. Then some more minutes go by and the fans ramp up to very noticeable and annoying speeds.

Thanks so much for the nice note and happy to help! I think you just gave me an idea on your post and I'd like you to try something else here (noted in the next paragraph). Also, that's perfect on the cooling setup you have, I just wanted to ask in case - I also didn't think that would be the issue for you since you opened the system up and were working on it etc., but sometimes like to point that out for anyone else that comes across these threads. 

With that said, since the system was quieter on battery and changed when the AC adapter was attached, can you try this next, - also, I don't recall if this changed on your model (and is hidden/removed now) but thought it would be worth checking. Anyway, did you happen to check if you can change the cooling mode for AC vs Battery mode? You might have it set on passive for battery and active for when the system is plugged in.  

To check if this option is available - Right click your battery icon on the taskbar, click power options - Once the window opens next to the current selected plan click "change plan settings". On the next window that opens click "change advanced power settings". Finally in the next window, you should see an option for processor power management, expand this section and you should hopefully see - system cooling policy. Under this option you will have one for battery and one for ac adapter, Right now it might say passive for battery and active for when the system is plugged in. Change the plugged in option to passive, and then click apply and then ok. It also might be worth restarting the PC after making this change. 

*Please note that if this option is there I would only do this when you aren't using the system for aggressive tasks, like if Idle or doing light things you could change it, and then when you need more cooling/power can change it back or even make separate power plans to make changing it easier. 

Let me know if this option is there or if it helps at all.  

Oh and sidenote, I started using the drivers tool in SupportAssist as well as the optimizer tool in the hopes that a new driver would fix my problems. There were 8 drivers and updates but there hasn't been a change in the situation.

I totally understand, it's very common for most people to be unaware of the air intake in their laptops. Everything was there as you said, and was set to Active for when the system is plugged in. I changed it and even enabled the other power plan as to quickly switch in case I need to do some heavy tasks. Then I restarted the PC which greeted me with pretty silent fans (not completely though) and I had some hope, only for it to be crushed when the fans started ramping up again. I'm at a loss for words. You've tried so many different things, maybe I should just accept that 3 and a half years just did this to the PC even though I does seem kind of odd how in the space of one week it went from dead silent when using multiple apps and desktops with 2 screens to really loud fans with no programs running. The CPU temps are also kind of worrying, but maybe they were always like this and I only started checking now due to the fan situation.

Thank you for your dedication and let me know if you think of something else. And don't worry if you can't, you've already done plenty.

Woah I think I just noticed something. Since your message I've been regularly checking Task Manager for CPU-hungry processes and I think I may have found one. I opened Task Manager and for a split second I saw "system interrupts" with bright orange on the CPU column maybe using about 50% before it dissapeared. I googled the name of the process and it seems many other people have had problems with this process taking up CPU processing power. I found a pretty complete blog post that gives plenty of explanation on the possible fixes to the issue. Maybe you can take a look and tell me what's worth trying out? I'm really hoping this is it.

Thanks for any and all advice you can give.

P.S.: Now every time I open up Task Manager for the first second or so the total CPU usage is >50% but then drops down to around 5 - 10%

@manut99,

try to disable and then re-enable the nvidia driver in the device manager... I have exactly the same issue as you can see in this post , and this workaround works for me. A question: do you start your laptop with a dock station or other kinds of stuff connected to the usb-c port?

g.