Hi i know this may sound daft but i have taken the cover off my 55 4.2 l322 to see what make the compressor is as i have air suspension fault. Seen theough various work done on the car in the past its had some new struts and height sensors done.
So I am thinking its got to be that seal around the piston, trouble is when i looked at it i cannot see a make on it like amk or hitachi. Could any say what make it is from the photo much appreciated!

Click image to enlarge

Click image to enlarge

Google that part number gives bits for hitachi so its a hitachi compressor

Thanks mate, I’ll look for the parts👍