E 250 Van L6-300 4.9L (1984)
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Vacuum Tank: Description and Operation
Fig. 37 Vacuum reservoirs
The vacuum reservoir, Fig. 37, used on some vehicles, acts as an accumulator and prevents sudden drops or rapid fluctuations in a vacuum signal during
acceleration. If vacuum in the reservoir leaks more than 1/2 inch Hg in 1 minute, the reservoir is defective and must be replaced.