New CPU cooler installed & smaller heatsink re-seated; now fans LOUD and display blank!


May 20, 2017
System Specs:
HP Compaq Elite 8300 USDT/USFF with i5-3470s and 16gb RAM
Windows 10 on 120gb SSD; 250GB HDD

Hello all, I have a HP Compaq Elite 8300 USDT/USFF pc- the reeeealy small one. I have it running 24/7 as a media server, and since heat kills, I wanted to upgrade the cooling a little bit. Since the form factor is so small, and a replacement/larger case is out of the question (as well as liquid cooling for now), I purchased the Noctua Low-Profile NH-L9I heatsink and fan.

While I was inside the PC, I mistakenly thought it would be a good idea to remove the other smaller heatsink with the Z-clip and replace its thermal paste. I didn't realize this was not a regular paste setup and it's actually glued on, until it was too late. I believe this heatsink is for the chipset/northbridge (correct me if I'm wrong?) but I did the best I could and applied paste and clipped it back on. It moved a little, but seemed like it would be okay.

Moving on to the cooler, the 8300 USDT has a passive cooler mounted to the processor and a small PWM fan in front and back of the case for cooling. I had to modify the case slightly to accomodate the new setup, which included hammering down the pieces of the back/bottom of the case that the OEM cooler mounted to, effectively removing my ability to go back to stock without figuring out how to re-mount the old cooler.

Anyway I get the cooler mounted, and use a PWM fan cable splitter to wire in the new fan with the front fan. I get everything all zip-tied up and perfect, and plug the beast back in. Immediately I notice that my monitor isn't doing anything (LCD tv connected by a DisplayPort-to-HDMI converter dongle) and then all three fans start spinning so loud it sounded like a jet engine taking off! This PC is quiet as heck, so this caught my attention real fast! I immediately shut it down. I remove the new fan and splitter, and just keep the two original fans connected to see what happens. Turn it back on, and the same sequence of events happens- nothing on the screen, and just eventually the fans go crazy.

I then wonder if maybe the CPU cooler is not making good contact with the processor? So I take it allll apart, remove the cooler and look at both sides- the TIM is perfectly spread, and I could tell it had made great contact. So it isn't that, and the PC barely had time to heat up! So then I wonder if I effed-up with putting the TIM under that small heatsink; so I take that off, clean the TIM off it and the exposed die underneath, and place it back on. I also pressed the BIOS reset button just in case, and tried it again. SAME THING!!

Tonite after work, I plan to hook up a monitor to the VGA port and see if anything can be seen on the monitor that way. As suggested on another site, I will also be replacing the CMOS battery and checking/re-seating the processor. But does anyone else have any suggestions? I am highly pessimistic that the battery and processor seating are the issue, and I really rely on this PC and don't have a lot of money to keep buying stuff to try and see if it fixes the problem. I've googled and I can't even be sure that the small heatsink is really on a chipset or northbridge; could it really be for the integrated graphics instead, and that's why I can't see anything on the monitor? HP's board layout pic identifies everything else BUT that. So any help is appreciated greatly! Thanks in advance!!!
>>I didn't realize this was not a regular paste setup and it's actually glued on, until it was too late.

This part got my attention.
My guess is that you damaged the mobo.

Did you have to apply a lot of force to remove the heatsink from the chipset?

You may have to get a used mobo from Ebay.