refrigerent Vents out from the back of the compressor

[mo5005]

1988 Volvo 760 T 190K

What the heck is going on? I have no leak. i vacuumed the system. I changed the accumulator, orifice tube (non-vov), and condenser. I go in and try to put in 2 pound of refrigent through from the cans from auto zone. and as i'm going on the last can its blows all of it out from the back of the compressor. what is going on!? i just lost 35 bucks worth of R134a!!

HELP!!!

 

[Hodginsa]

Theres a shredder valve like thing at the back of the compressor, maybe when you vacuumed the system it popped in and got stuck open. Letting all the new stuff out.