Get the MitiVac, too -- it's a hand pump plus gauge, and is very handy for vacuum problem troubleshooting.

You can also have the check valve at the booster fail -- it's the fitting in the line or on the booster itself. The grommet on the booster can go bad, too, causing a massive leak.

The plastic multiport fitting in the middle of the main line can crack, too. Not available as a separate part, you have to buy the whole line, but it's not expensive.

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!