2003 Dodge Durango AC gets warm when the rear AC is on

I could not find the window, I looked on top of the I believe the accumalator but did not see anything. I added about half a bottle and the ac clutch disengaged and started to cycle. After I shutdown and restarted I had oil and freon venting out of the back of the compressor whenever it would engage. I shut it down and inspected the tube connections to the compressor they looked fine, I did see a hole on the back of the compressor where I think it was venting from. When I get more time I will have to clean all the oil up and I will take a better look with the intake off. I spoke to a mechanic friend of mine who never heard of a compressor with a 'blow off valve' I did vent the system on the low pressure side and retried the ac and everything is working now I get cold air with both the front and the rear ac on. Have you ever heard of the compressor venting or did I blow out a seal?