Chris:

Servo is shot then, most likely. Or a hose is off the switchover valve.

The orifice is to allow partial servo position, I think. Slows the diaphram action down. I think this servo is a dual diaphram, too, but I could be wrong.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!