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Old 04-12-2005, 03:18 PM   #1
Scooby Newbie
Member#: 73034
Join Date: Oct 2004
Location: Rochester, NY

Default Vacuum Test

Did a search and came up with a bunch of info but not a step-by-step approach. Just need to know how to perform a vacuum test (options, tools, procedure...). Anything that may help as I would like to get this done today or tomorrow. Thanks
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Old 04-12-2005, 03:56 PM   #2
Scooby Newbie
Member#: 72021
Join Date: Oct 2004
Location: BARBADOS


5. Intake Manifold Vacuum
1) Warm-up the engine.
2) Disconnect the brake vacuum hose and install
the vacuum gauge to the hose fitting on the manifold.

3) Keep the engine at the idle speed and read the
vacuum gauge indication.
By observing the gauge needle movement, the
internal condition of the engine can be diagnosed
as described below.

Vacuum pressure (at idling, A/C “OFF”):
Less than −60.0 kPa (−450 mmHg, −17.72

Diagnosis of engine condition by measurement of manifold vacuum
Vacuum gauge indication Possible engine condition

1. Needle is steady but lower than normal position. This tendency
becomes more evident as engine temperature rises.
Leakage around intake manifold gasket or disconnection or
damaged vacuum hose

2. When engine speed is reduced slowly from higher speed,
needle stops temporarily when it is lowering or becomes
steady above normal position.
Back pressure too high, or exhaust system clogged

3. Needle intermittently drops to position lower than normal
Leakage around cylinder

4. Needle drops suddenly and intermittently from normal position.
Sticky valves

5. When engine speed is gradually increased, needle begins
to vibrate rapidly at certain speed, and then vibration
increases as engine speed increases.
Weak or broken valve springs

6. Needle vibrates above and below normal position in narrow
Defective ignition system or throttle chamber idle adjustment
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