26 MS 290, MS 310, MS 390
– Carry out preparations, b 6.2.1
: Connect pressure hose to nipple
(arrow) on test flange.
VA
209RA029
: Close vent screw (1) on the
rubber bulb.
: Pump air into the crankcase with
rubber bulb (2) until the gauge (3)
indicates a pressure of 0.5 bar.
If this pressure remains constant for
VA
249RA012
2
1
3
at least 20 seconds, the crankcase
is airtight.
If the pressure drops, the leak must
be found and the faulty part
replaced.
To find the leak, coat the suspect
area with oil and pressurize the
crankcase again. Bubbles will
appear if a leak exists.
– Repeat the pressure test if
necessary.
– After finishing the test, open the
vent screw and disconnect the
hose.
– Continue with vacuum test,
b 6.2.3
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.
A test can be carried out with the
vacuum pump to detect this kind of
fault.
– Carry out pressure test, b 6.2.2
: Connect suction hose of vacuum
pump 0000 850 3501 to nipple
(arrow) of the test flange.
VA
209RA029
: Close the vent screw (1) on the
pump.
: Operate lever (2) until pressure
gauge (3) indicates a vacuum of
0.5 bar.
VA
135RA061
2
1
3
6.2.2 Pressure Test 6.2.3 Vacuum Test
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