After disconnecting pipes and hoses, immediately close the openings to prevent moisture from entering the system.
Use new O-rings for each assembly.
When connecting the tubes, apply grease to the location shown in the figure. Do not allow grease to get on the threads.
The sealing rings must be installed close to the tube protrusion.
Tighten the union nut after the tube is fully inserted into the coupling (the sealing ring will no longer be visible).
If a leak is detected in the connection, disassemble it and replace the sealing ring, then tighten it again to the required torque.
(The source of the article is on the website: www.nissanbook.ru)