Can you run a pc without a CPU cooler?

Yes, you could turn it on but as soon as it starts overheating it would do a thermal shutdown to avoid major damages. Without a Cooler, the CPU would heat up to a point it starts burning and may even result in damaging the motherboard. In the worst case, you can even witness smoke coming out of your CPU and it will no longer be of any worth. However, usually, CPU would keep working but there would be a decrease in its performance and lifespan.

The entire process won't take more than a few minutes. Most PCs won't start in the first place as they have detected that the CPU cooler isn't connected or once the PC starts just after some minutes you would see "CPU FAN ERROR!"

According to a poll held at overclock.net, 86.6% of people voted that the pc might not stay up for long, and it isn't a good idea to run a pc without a cooler.

In case, you currently don't have any CPU cooler available, you can safely run your PC for around 2-3 mins, you can also add an external fan directed towards your pc after removing the side panel, making sure it is well ventilated and chances of overheating are minimized!