PC instantly shuts off after pressing power — oily residue found on GPU and motherboard

Hey everyone,

I’m trying to diagnose a power issue that started suddenly. When I press the power button, the system powers on for about half a second, then shuts off completely — no fans spin up.

Here’s my setup:

• CPU: i5-10600KF
• Motherboard: ROG Strix Z490
• GPU: ASUS Dual RX 5700 EVO OC
• PSU: tested with another known-good unit — same result
• RAM: tried different sticks and slots — no change
• GPU: tested with another card — same issue
• All power connectors (24-pin, 8-pin CPU, GPU 8+6 pin) fully seated
• Cleared CMOS multiple times
• Repasted both CPU and GPU

During inspection, I found an oily residue on both the GPU PCB and the VRM area of the motherboard. I wiped and brushed it with 70% isopropyl alcohol pads until the surface looked dry and matte.

Now the system shuts off instantly even without CPU, GPU, or RAM installed. I also noticed the power button no longer works, and even manually shorting the power switch pins doesn’t turn it on — only touching the clear CMOS pins makes the board power up for about half a second before it shuts off again.

At this point, I suspect something shorted in the motherboard’s VRM or BIOS circuitry, possibly caused by that oily contamination.

Questions:

1. Could the residue have caused a short that permanently damaged the board?
2. Is there any other area worth re-cleaning or checking before assuming the motherboard is dead?
3. Any chance of reviving it with deeper cleaning (ultrasonic or 99% IPA)?

Any advice from those who’ve dealt with similar instant-shutdown cases would be greatly appreciated.