What else should I look for to stop the air leak on the rear air springs system? on 2002 Ford Expedition

I changed the 2 rear air springs and solenoids on an Expedition 4x2. What else should I check or replace to stop the system from leaking air? The air springs inflate, but within minutes, deflate.

Asked by for the 2002 Ford Expedition
Air lines could have a leak or you might have a faulty compressor.