air compressor slow to build air

I really hate to admit how dumb I am, but will do so in the aim to help others... I have come to the conclusion that I had my problem backwards. for a couple years at least my air would stay at 120. on both gauges. they did not go below 120 unless I was on the brakes, & then right back to 120. the air dryer, or purge valve would purge ever few seconds. when I fixed the leak the system starting working correctly, but as I was used to it working like it was before I thought the right way being different was the wrong way. as soon as I saw it NOT staying at 120 I thought I must have done something. will tell you one thing. you have to have truck running to check leak on compressor. with my truck off the leak would not show, or show very small leak of bubbles only after 10-15 minutes. with the truck running, the soapy water bubbled out like crazy. turned truck off & the leak diminished greatly. now when my problem first started over couple years ago. I had rebuilt compressor put on, new air govenor. still the same air pressure at constant 120 & same purging. jut gave up on it & & figured I had to live with it, as maybe this is normal. at least I learned something from this.