Go buy a MitiVac hand vac pump at the parts store. Costs about $35 and is worth every penny.

Once you have the pump, you have both a portable vac source and a gauge. Attach pump to the shutoff and pump down -- must hold vac indefinitely and must pull the stop lever down.

You must get at least 11" vac at the connection for the brown vac line on the main line between the vac pump (front of the engine) and the brake booster.

Most likely, if this suddenly appeared, you have dislodged the brown vac line from the main vac supply line.

The rubber connectors are probably all in questionable shape by now -- they either get soft and perforate or get rock hard and shrink, then get loose or crack and leak. The orifice in the connector can also get plugged, so you have no vac, or the plastic fitting can crack, causing a leak. The fitting in the main line isn't available separately, you must buy the whole line.

Get the MitiVac, it makes finding vac leaks easy. Note that a major leak anywhere can cause you trouble!

Peter

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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!