ENGINE DIVISION SERVICE MANUAL
ADDENDUM NO. 3
VACUUM SYSTEM HOSE LEAKAGE TEST
Perform engine vacuum system hose leakage test as follows:
1. Install vacuum gauge and tachometer. Care should be taken to insure that vacuum gauge is connected to manifold vacuum and
not to some other vacuum such as ported spark or EGR signal vacuum.
2. Start and run engine until normal operating temperature is reached. Then, with engine running at curb idle speed, record vacuum
gauge and tachometer reading (baseline).
3. With engine running at curb idle speed, remove each vacuum hose (one at a time) from vacuum source and plug source. When
removing vacuum hose to distributor on engines which have straight manifold vacuum advance, apply at least 15 In.Hg. vacuum
to vacuum advance using hand vacuum pump SE-2499 to prevent change in spark timing during test.
4. As each vacuum circuit is checked, record vacuum gauge and tachometer reading. If no change in reading is observed (from
baseline), no vacuum leak exists in that particular vacuum hose circuit. If a change in reading is observed, a vacuum leak does
exist in that particular vacuum hose circuit and can be located as follows:
a. Remove plug and reinstall vacuum hose.
b. Remove other end of same vacuum hose at next downstream connection and plug.
c. Record vacuum gauge and tachometer readings.
d. Repeat steps 4a through 4c at each hose connection until leak is isolated. Leak is isolated to last component checked when
reading returns to baseline value. Replace leaking hose(s) or component(s) identified.
5. Continue procedure until the integrity of all vacuum circuits is verified or restored.
CGES-215 - Page 47
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