OK, so I have replaced the compressor mounts with new and dished the washers which were flat. They are orientated correctly, like so... >|<
The vibration is inaudible outside the vehicle and is quieter inside but still annoyingly audible. It isn't noticeable when on the move.
Any ideas on how to improve things further? Are there improved mounts available? The pump is 3-4 years old, would a rebuild be likely needed/useful? It isn't an OEM pump I don't think.
Have a look at Storey Wilsons video.
He is the guy that created eas programming software for pc's etc
another thing you can do is check that all the pipe work is not touching the car as this can produce a resonance sound that can go though the car .
If the pump has a black painted body, it is an OE one. If the motor is black but the compressor body is plain alloy, it is one of the Dunlop branded ones (which I doubt have ever been anywhere near Dunlop) being sold these days and they aren't as well made as the originals, bearing failures being quite common on them.
I built a bench test rig for valve blocks several years ago so I was able to run the whole system on the bench. I did several valve blocks along with rebuilt compressors at the time. There has been no need to run it since as I have enough spare blocks.
I can remember some of the compressors being particularly noisy and by a combination of fitting "penny" washers and turning the bushes upside down I eventually got it quiet. I can remember hammering the washers into a dish shape. It was easier to experiment with it on the bench.