2 questions.

1. Did you test cold or warm? If testing cold, I understand the thermostat will be closed, so only tests part of the system?

2. When you achieved the specified pressure, in your case 23 psi, how long did it hold this pressure?
How many minutes did you wait?
For example after 10 minutes, was it the same pressure, or did it drop and by how much?
This guide says it should not drop by more than 10% (2psi per minute). So does it mean 2 psi drop per minute is ok?
https://www.pelicanparts.com/techart..._Leak_Test.htm