Originally Posted by
mono
I agree Rivet,
Often caused by a lack of reservoir pressure which explains why the pressure fluctuates even though there are 2 system pumps (EDP/ACMP)
The reservoirs are automatically serviced with 25-50PSI air from engines (or APU if engines not running). If this is not occuring wouldn't you have the res pressure message on eicas?
If cavitation can indeed cause vibrations, I wouldn't search further for an explanation.