that could be a problem, if the dryer is now not sealing well. another possible problem is the 'new' dryer (from junkyard) is moisture saturated and plugged. There is a way to dry out the dessicant in the dryer, basically taking it apart and baking the beads at like 200 degrees or so for a little while... Look in the tech section for a procedure, if not here over at LoL.
Also, make sure the seal between the compressor and dryer is good. Also the replacement compressor may have a leaky vent valve (rusty usually). If so, I would take it back to the yard and stuff it up part of the yard manager's body that never should see daylight. They sold you a defective part. The vent valve or soleniod is part of the compressor. if its like my compressor (a 91), there is a small panel (or was it the whole top plate?) that can be removed that will expose the vent valve. but its not really repairable.