Brake booster testing.
 

Seeing I disassembled my original brake booster for metal plating 15 years ago & do not remember how I assembled it, I wanted to test it before installing brake fluid & creating a big mess later. So let me know if my precautionary testing seems about right, or if I am possibly missing something.........:confused:

I hooked up an external vacuum pump & brought it too 8-10 inches of vacuum. With no foot pedal force, I did a leak down test it will hold vacuum on its own, but does very slowly bleed off. Vacuum drops slowly from 10 inches to near zero in about 3-4 minutes.

I blocked off the push rod on the master cylinder side so it can not move forward. Then when I press the brake pedal I can hear the small amount of air go into the pedal side through the booster filter as the valve opens but the vacuum stays will stay consistent on the booster side. lastly, While holding the brake pedal firm, I did another vacuum leak down test & its the same as the first leak test. It holds vacuum, but very slowly leaks down after 3-4 minutes just like the first test.

So all seems good as far as I can tell, other than the slow leak down. I know I have worked on boosters that hold vacuum for far more than 3 minutes, but I am thinking this is still acceptable?

Any thoughts, or anything I am missing?