STIHL TS 460 33
5.5.3
acuum Test
1 = Lever
2 = Vent screw
Testing crankcase for leaks with vacuum
Oil seals tend to fail when
subjected to a vacuum, i.e. the
sealing lip lifts away from the
crankshaft during the piston's
induction stroke because there is
no internal counterpressure.
An additional test can be carried
out with the vacuum pump to
detect this kind of fault. The
preparations for this test are the
same as for the pressure test, see
5.5.1.
- Connect the vacuum pump's
suction hose to test flange
nipple.
- Close the pump pistons
vent screw.
- Pull out the pump piston
several times until the gauge
indicates a vacuum of 0.5 bar.
Note: If the pressure remains
constant or rises to no more than
0.5 bar, within 20 seconds, it can
be assumed that the oil seals are
in good condition.
However, if the pressure continues
to rise (reduced vacuum in the
crankcase), the oil seals must be
replaced, even if no leaks were
detected in the pressure test.
- Upon completion of test,
open vent screw again and
remove hose.
- Remove test flange and
reinstall carburetor, see 10.3.
- Loosen mounting screws
on exhaust muffler and
pull out sealing plate.
- Insert outer mounting screws
with lock washers and
tighten all mounting screws
to 10.0 Nm.
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