It's fixed, it was the mono valve. The little metal filter inside was completely clocked by dirt and rust accumulated over the years. A good clean and all is working again as it should.

__________________
1979 Black on Black, 300CD (sold), 1990 Black 300SE, Silver 1989 Volvo 780, 1988 300CE (vanished by the hands of a girlfriend), 1992 300CE (Rescue).