XPS 8940, Noctua NH-U9S CPU cooler upgrade

16mm M3 machine screws work perfectly fine. That's what I used to install the noctua on my G5 (same setup as the 8940). Another option is to use "headless" grub screws and the nuts included in the Noctua kit. Details here.

Yat another (much easier) option is to get the Vetroo V5 cooler, which is less than half the price of the Noctua and comes with all the screws you need to install it on the Dell. Performance and noise are on par with Noctua, from what people have been saying. 

Here's what I did...

https://youtu.be/nWOeO1Cfva0

Thank you, I actually looked at your video before I decide to change to a Noctua NH-U9S, it was really helpful, however I am locate in Canada, and I believe another youtuber mention being unable to get the screw without the head. Would like to know where can I get those M3 25mm from you video, thank you

Thank you very much, sorry if I am being a bit annoying, I went Canada bolts and try searching for the M3 25mm, but cannot find the one with no head that you use in the video. Is there another name or what type of head should I search for. I am not a machine guy, that why I went with the dell pre-build, but wasn't expecting all those issue with Dell. Thank you

@Mel628  I'm in Canada too and I used canadabolts.ca to get the screws. Hardware stores (at least those in the Montreal area) didn't have the right ones. Canadian Tire only has M3s up to 10 or 12 mm, if I remember correctly. 

Regarding the Vetroo V5, there are users on the forum who have installed it and I haven't read complaints about it not fitting (example). However, here in Canada the price is not far from the Noctua. In the US it's less than half.

I am in Canada too. I used these screws for Noctua NH-U9S. 

50 Pcs M3-0.50 x 20mm Button Head Socket Cap Screws, Passivated 18-8 Stainless Steel, Allen Hex Drive, ISO 7380, by Fullerkreg,Come in an Easy-use Storage Case https://www.amazon.ca/dp/B07H183MVP/ref=cm_sw_r_cp_api_glt_i_NSVYYC6HMZVG20GJR373?_encoding=UTF8&psc=1

@Mel628, yesterday I bought M3x25mm grub screws from a Chinese seller on eBay:

M2/M3/M4/ M5/M6/M8 Stainless Steel Grub Screws Flat Point Hex Socket Set | eBay

Of course, it hasn't arrived yet and it'll take me several weeks to get them, but it only costed me four loonies and change, so I'm ok to wait. For that amount, I'm willing to take a chance.

@Mel628 I actually got regular M3 16mm screws from canadabolts, not the headless ones. I see @CowBird and @av-user recommended some places where you can get headless ones. You might want to also email canadabolts and ask if they can get those for you. Might be faster than ebay. I got mine in 3 days or so.