777 SERVICE MANUAL HYDRAULIC SYSTEM
Manitowoc Published 10-01-2012, Control # 045-08 2-7
2
Changing Oil
Drain and refill hydraulic system every 1,000 hours or
semiannually, whichever comes first, unless an alternate
interval is established through an oil analysis program.
1. Operate crane until hydraulic oil is at normal operating
temperature. This will help prevent impurities from
settling in system.
2. Stop engine.
3. Open drain valve (Figure 2-4, View A) on hydraulic tank
to completely drain tank. Catch oil in suitable containers.
Tank capacity is 120 gallons (454 liters).
4. Clean all dirt off access covers on tank. Remove all three
covers. Take precautions to prevent dust and wind-
blown dirt from entering tank while covers are off.
5. Flush out any sediment inside tank.
6. Using a wrench, remove Filter 5 from inside tank. Filter 5
is accessible through cover on front of tank (Figure 2-4,
View C).
7. Soak Filter 5 in clean, nonflammable solvent. Brush off
outer surface, and flush from inside out. Replace if
damaged.
8. Reinstall Filter 5.
9. Use new seals and securely fasten access covers to
tank.
10. Clean fill cap assembly (Figure 2-1).
11. Replace all filter elements (Figure 2-2).
12. Open shut-off valve at tank (Figure 2-4, View C).
13. Check that engine clutch is engaged.
14. Open shut-off valve at Filter 1 (Figure 2-2, View B).
15. Loosen vent plug at Filter 1 (Figure 2-2, View A).
16. Loosen vent plugs at Filters 3 and 4 (Figure 2-2).
17. Fill hydraulic tank to proper level as indicated on decal
next to tank sight gauge (Figure 2-4, View B). Use
proper hydraulic oil (see Lubrication Guide in Section 9
of this manual). Filter oil with a 10-micron element as oil
is added to tank.
18. Monitor vent plug at Filter 1 (Figure 2-2). Oil will flow by
gravity to vent plug. Tighten vent plug once oil appears.
19. Disconnect engine fuel solenoid electrical plug from
junction box on right side of engine (Figure 2-5). This
step is required to keep engine from starting while filling
Filters 3 and 4.
20. Crank engine for 10 seconds. Oil should appear at vent
plugs at Filters 3 and 4 (Figure 2-2). If oil does not
appear, crank engine for 10 more seconds. Tighten vent
plugs once oil appears.
21. Reconnect engine fuel solenoid electrical plug to
junction box on engine (Figure 2-5).
22. Start and run engine at low idle for 10 – 15 minutes to fill
all lines with oil and bleed any remaining air from
system.
23. Stop engine and fill hydraulic tank to proper level as
indicated on sight gauge (Figure 2-4, View B).
NOTE: If hydraulic system is extremely dirty (gum or
lacquer formation on parts indicated by erratic,
jerky, or sluggish operation) repeat Changing Oil
procedure after 48 hours of operation.
CAUTION
Equipment Damage!
Be sure to drain oil from and add oil to hydraulic tank, not
fuel tank. The two tanks are next to each other on right
side of crane. Hydraulic tank is right tank.
Fuel Solenoid
Electrical Plug
Junction
Box
FIGURE 2-5
P438
Right Side of Engine
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