Red:

Two things:

One: the vac switch on the driver's door can go bad and leak down, sometimes in only one postion (lock or unlock).

Two: A bad check valve will vent off the vac reguardless of the condition of the rest of the system.

Make sure you hold vac with the check valve in the circuit (use a T for the hand pump). We had to replace both on my brother's 300D, they buzzed when the engine was shut off.

If the locks leak down, then only that check valve is bad, probably.

Otherwise, if it only leaks down locked or unlocked and not both, then you still have a leaky diaphram somewhere.

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!