I recently noticed the click sounds from the left up corner of the macbook pro body when I put the laptop on a stand with tilt. This drives me nuts so I decided to investigate by myself since my apple care is expired. Originally I thought it was caused by fans so I opened it and removed both fans, but the sound still exists. After removing the cooling tube which attaches to both gpu and cpu, the sound is completely gone. I just don't know why the cooling tube makes the noise and I checked the tube, there is nothing inside it. Is the electric arc causing the sound? I really don't know why... Btw, when I put macbook pro on the flat table, the click sound goes away immediately. Can anyone please put it on a stand with tilt to try if the issue also happens to your laptop? Any idea why? Thanks in advance.