TST-020 PT-AIR
– REV. 2017-246
Page 1 of 14
SYMPTOMS OF VACUUM LEAK
A severe leak
is evidenced by a lifter’s inability to draw full vacuum while attached to a clean,
smooth, nonporous surface. In such cases, the vacuum level shown on the vacuum gauges will be
less than 16" Hg [-54 kPa], the red zone of the vacuum gauge.
A moderate leak is indicated if the lifter loses more than 4" Hg [-13.5 kPa] in 5 minutes during a
vacuum test when the power is off. This amount of lost air is serious enough to warrant repairing
the lifter’s vacuum system.
DETERMINING LEAK EXISTENCE
To determine if lifter has a vacuum leak, perform the Vacuum Test as described in the Maintenance
section of
lifter’s instruction manual.
During vacuum test it is recommended that you take notes on amount of air lost in time increments
(i.e. “Lost 5" Hg [-17 kPa] in 5 minutes”). This assists in diagnosing the location of the leak because
there may be more than one component leaking vacuum. For example, if an isolated section tests
positive for a leak but the leak rate is less than that of the whole lifter, then there is still one or more
vacuum leak elsewhere in the system.
ADDRESSING LEAK
If the leak is sufficient to warrant repair:
Locate the cause of leak beginning by inspecting the vacuum pads, fittings and hoses of the entire
vacuum system. Look for contamination, cuts or abrasions on pad faces, cracks in the pad suction
stem, cracks, abrasions or cuts in hoses, damaged fittings and loose hoses at connection points.
If leak is severe, the cause is often a visibly damaged part.
Caution:
Do not apply soapy water to fittings or vacuum hoses in an attempt to find leaks, since it
will only be drawn inside the vacuum system.
If
the leak’s source is not immediately evident, the various sections of the entire vacuum system
must be systematically isolated and tested to determine the leakage point. The process to
accomplish this is described in the tests to follow.
Note: The information gathered when performing a vacuum test is only valid if the tools used to
perform the test are accurate. Be sure that the tools used are capable of completely sealing the
isolated parts of the vacuum system when tested.
Recommended tools
1
: Plugs for hoses and fittings, ball valve with vacuum gauge attached,
appropriate hose adapters and extra vacuum hose.
2
1
If needed, test equipment is available from Wood’s Powr-Grip. Contact us for additional information.
2
Procedure assumes operator has access to appropriate tools
