A/C slow leak down, compressor shaft seal?

[ramiron]

System leaks down and quits working after about 2-3 days after charging the system. I ran a bubbles leak test with a charged system, no leaks found. I charged the system with air to 70 psi, using gauges, and monitored for 3 hours. There was no apparent drop after 3 hours. After approximately 15 hours there was about 2+ or so pounds drop. Then over the next 8 hours it dropped from about 67psi to 60psi, apparently an accelerated rate. It seems that maybe a seal holds under higher pressures, then leak more rapidly as pressure on it drops? The system doesn't appear to loose all pressure. Finally my question,... is this typical of a compressor shaft seal? I have not checked the evaporator (1+ yr. old) and I have not leak tested this shaft seal. Can the shaft seal be bubble tested w/o causing problems by spraying bubble solution into the shaft area? How tough is replacing the seal, I have removed the clutch already to replace the clutch bearing?

Thanks in advance for the help.

[ramiron]

FYI: It did end up being the compressor shaft seal. Word of Caution: I learned from a Haynes manual that charging a system with air can be DANGEROUS! I don't know how much pressure it takes, but the manual says it creates a flameable possibly explosive gas. You should use Nitrogen not air to pressurize a r-134a system, which I didn't know.

Back to the problem, I found the leak with the penlight style UV light. Pull the ac clutch and you can shine the uv light on the seal, there was no doubt about it with the dye showing up.
Be safe, what you don't know can hurt you.