TST-011
– Rev. 2013-049
Page 3 of 12
SYMPTOMS OF VACUUM LEAK
Severe leakage is evidenced by a lifter’s inability to draw full vacuum while attached to a clean,
smooth, nonporous surface. In such cases, the vacuum pump will run continuously and the vacuum
level shown on the vacuum gauge will be less than 16" Hg [-54 kPa], the red zone of the vacuum
gauge.
Moderate leakage is indicated by intermittent cycling of the vacuum pump and the (red) low vacuum
warning light during a lift. If the vacuum generating system turns on more than once every 10
minutes, leakage is serious enough to warrant repairing the lif
ter’s vacuum system.
To determine if your lifter has a vacuum leak, perform the Vacuum Test as described in the
Maintenance section of your instruction manual.
When you perform the vacuum test, we recommend that you note the time and leakage rate, such as
“lost 5" [-17 kPa] in 10 minutes”. This information can assist in diagnosing the location of the leak
because there may be more than one component leaking vacuum. For example, when you are
performing maintenance, if an isolated section tests positive for a leak but the leakage rate is less
than that of the whole lifter, the indication is that there is still one or more vacuum leak elsewhere in
the system.
If the rate of leakage is sufficient to warrant repair, proceed as follows:
To locate the cause of leakage, begin by inspecting the vacuum pads, fittings and hoses of the entire
vacuum system. Look for contamination, cuts or abrasions on pad faces, cracks, abrasions or cuts in
hoses, damaged fittings and loose hoses at connection points. If leakage is severe, the cause is
often a visibly damaged part.
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 source of leakage 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.
Please note, the information that is gathered when performing a vacuum test is only valid if the tools
used to perform the test are accurate. Be sure that the tools you use are capable of completely
sealing the isolated parts of your system when tested. Recommended tools, in addition to an
appropriate test surface, are plugs for hoses and fittings, a ball valve with vacuum gauge attached,
and extra vacuum hose. This procedure is written with the assumption that you have access to the
appropriate tools.
If needed,
test equipment is available from Wood’s Powr-Grip Co.
A set of screwdrivers may also be needed if the valve enclosure or pump cover needs to be removed.
Note: Always proceed with caution when removing the vacuum generating system cover. Since
wiring is connected to components in the cover, gentle removal is recommended so as not to damage
the attached wiring.
Note: When removing a hose from a fitting, take care to avoid damaging the barbs of the fitting the
hose is attached to. Cuts or nicks in fitting barbs can create a leak that did not previously exist.
Additionally, if a hose is removed from a barbed fitting, cut approximately ¼" [6 mm] off the end of the
hose before reinstalling it on the fitting, in order to remove damaged hose ends.
