A/C only leaks with vacuum?

2008 SKODA OCTAVIA
120,000 MILES • 1.8L • TURBO • MANUAL
Avatar
JACK1976
Hi, my A/C only leaks with vacuum but not with pressure (15 bar nitrogen). I think it is odd but maybe you know, how this can happen? And how to detect, where the leak is?
Thanks a lot.
Best regards,
Jack
Jun 22, 2026 at 6:51 PM
Advertisement
Avatar
STRAILER
  • ✓ASE Certified Mechanic
  • 54,480 POSTS
  • ASE Certified Mechanic
Yep, this can happen when the front compressor seal goes bad, common. I would still run a leak test with a small amount of refrigerant. Please follow this video to help confirm the failure.

https://www.youtube.com/watch?v=yrhWKlQEPWw

Please go over this video and get back to me.

Jun 24, 2026 at 1:39 AM
Avatar
JACK1976
  • MEMBER
  • 2 POSTS
Ok, thanks a lot.
The leak test shows no leak.
Is there any way to be sure its the compressor seal?
I mean, if the leak only occurs under vacuum, then nothing comes out to detect.
I have heard, that an O-ring can probably cause this too.
If it is the compressor seal, is it possible to replace it, or does the entire compressor need to be replaced?
Jun 25, 2026 at 7:43 PM
Avatar
STRAILER
  • ✓ASE Certified Mechanic
  • 54,480 POSTS
  • ASE Certified Mechanic
If it is the compressor seal, yes it needs to be replaced, let go at this another way, do you see compressor oil anywhere? Also, this can be the condenser or evaporator core. Use a flashlight to inspect for oil, this can guide us to the leak. Please upload a short video in your response of the problem, so I can see what's going on :)
Jun 25, 2026 at 10:06 PM
Join 2CarPros for free, one of the most advanced car repair communities on the internet. From first-time drivers to seasoned mechanics, everyone is welcome to reply, share details, and get better answers. You can add a temporary image or video first; uploads are limited to 20 MB.
Ask a Free Question
Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.