Thank you both. I will check the Library. The problem is not about leaking. The AC was not working properly. Sometimes it worked, sometimes it did not send cool air, so I took it to a shop. They evaluated and said that I needed to replace the Expansion valve and the Evaporator. They wanted to charge me more than $1000 to do it, and since I don’t have that amount of money, I decided I am going to do it myself.