Go the o auto parts store and buy a MitiVac hand pump. It has a gauge, so you can hook it up and see how much vac you have in the lines, can manually pump down systems, etc.

If the booster isn't working, either the pump itself is shot (and this may be a simple repair like a broken check valve) or the booster or booster check valve is bad. Doesn't take much vac to run the booster.

Note that if you have good power assist above 1000 rpm but not below, you have a bad booster or booster check valve for sure -- once the booster is pumped down, it should stay pumped down until you use it. If the boost goes away below 1000 rpm, something is leaking.

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!