I have an 04 4.4 X5 with rear sport self leveling suspension. The back end of course is sagging real low.

I have checked all corresponding fuses in the glove box and in the rear.

I have made sure the bags, resoviors, and lines are not leaking with soapy water the best I can

I removed both rear tires and angled the sensors as if it were high or low with car on but not started

I even went crazy and took off the relay at the pump and jumped two pins, which the compressor came on, BUT as soon as I disconnect the "jump", I hear a lingering hiss within or around the compressor and it sounds every so slightly that the hissing may even be occurring when it is on. I checked and tightened all hoses connected and still the rear does not rise. Please help me!