NO. 120 MOTOR GRADER When Required Caterpillar

When Required
1.1. (50)Rear Axle Housing
2.1. (51)Front Wheel Lean Control Housing
3.1. (52)Transfer Gear Housing
4.1. (53)Circle Reverse Control Housing
5.1. (54)Tandem Drive Housings
6.1. (55)Blade Lift Control Housings
7.1. (56)Circle Center Shift Control Housing
8.1. (57)Steering Gear Housing
9.1. (58)Center Shift Rack - Split Rack
10.1. (59)Blade Circle
11.2. Check Adjustment:
12.1. (60)Engine Air Intake System
13.2. Servicing Primary Element:
14.2. Servicing Secondary Element:
15.1. Cleaning Air Cleaner Elements
16.2. Pressure Air - 100 PSI (7 kg/cm<sup>2</sup>) Maximum
17.2. Water-40 PSI (3 kg/cm<sup>2</sup>) Maximum
18.2. Detergent
19.2. Checking Element
20.1. (61)Diesel Fuel System
21.2. Primary Filter Element
22.2. Final Filter Element
23.2. Priming the Fuel System
24.2. Fuel Tank Filler Strainer
25.1. (62)Cooling System
26.2. Cleaning the Cooling System
27.1. (63)Ball And Socket Joints
28.1. (64)Wheel Brakes
29.1. (65)Parking Brake
30.2. Handle Knob
31.2. Linkage
32.1. (66)Shear Pin
33.1. (67)Cutting Edge And End Bits
34.2. Cutting Edge
35.2. End Bits
36.1. (68)Blade Lift Worm Gears
37.1. (69)Blade Lift Brakes
38.1. (70)Flywheel Clutch

(50)Rear Axle Housing

1. Check oil level at full plug opening at rear of axle housing.

2. Remove plug from filler neck.

3. Maintain oil level to top of filler neck. Clean and install plug.

(51)Front Wheel Lean Control Housing

Maintain oil level to bottom of filler plug opening.

(52)Transfer Gear Housing

Maintain oil level to bottom of filler plug opening.

(53)Circle Reverse Control Housing

Maintain oil level to bottom of filler plug opening.

(54)Tandem Drive Housings

Check oil level in each tandem. Oil level should be up to the FULL mark on plunger gauge.

(55)Blade Lift Control Housings

One housing on each side of machine. Maintain oil level to bottom of level plug opening. Filler plug opening is on top of housing.

(56)Circle Center Shift Control Housing

Maintain oil level to bottom of filler plug opening.

(57)Steering Gear Housing

Maintain oil level to bottom of level plug opening of manual type. Maintain level 11/2 inches (38 mm) below opening in hydraulic type.

(58)Center Shift Rack - Split Rack

1. Set rack so 1 inch (25 mm) of rail shows at right of rack. Remove center shift link pin and pry rack away from pinion.

2. Check clearance between right front half of rack and rail. Clearance at tightest point should be .010 to .030 inch (0,259 to 0,772 mm).
3. Set rack so 1 inch (25 mm) of rail shows at left of rack. Repeat step 2 to check clearance between left front half of rack and rail.

4. Run rack to extreme right and check clearance between left front rack and rail. Then run rack to extreme left and check clearance on right of rack and rail.


1. Remove shims from between rack halves to adjust. Three sets of .010 and .015 inch (0,254 mm and 0,3810 mm) shims are evenly spaced along rack.

2. Loosen rack bolts and ball stud. Remove equal thickness of shims from each set.

3. Tighten bolts and ball stud.

4. Check clearance.

(59)Blade Circle

Check Adjustment:

1. Center and level blade 3 to 4 inches (75 to 90 mm) off ground. Check clearance between each wear plate and top of circle.

2. Clearance should be .010 to .062 inch (0,30 to 1,57 mm). Rotate blade 360°. Stop every 90° and check.

3. Remove shoe bolts and remove or add shims to adjust clearance. Use new shoes if adjustment cannot be made.

4. Install shims and bolts. Check clearance as given in step 2.

5. Lower blade to ground and inch machine forward to put light load on front shoes.

6. Measure distance between O.D. of pinion and machined I.D. of circle. Measurement should be 1.90 to 1.92 inches (48,2 to 48,8 mm).

7. If distance is less than 1.90 inches (48,2 mm) replace front shoes and do steps 1 through 4.
8. Loosen locknuts of rear shoe adjusting screws.

9. Turn adjusting screws to move toe of each rear shoe against circle. (If shoes cannot be made to contact circle, install new shoes and perform steps 1 through 4.) Back adjusting screws out 1/3 turn and lock screws.

10. Check clearance between rear shoes and I.D. of circle. With light load on front shoes, clearance should be .030 to .090 inches (0,76 to 2,29 mm). If not, adjust shoes in or out, as necessary, with adjusting screws.
11. Rotate circle a complete revolution to make sure it moves freely.

(60)Engine Air Intake System

Service air cleaner elements if RED band in indicator is locked up. Stop engine.

Servicing Primary Element:

1. Remove cover and primary element.

2. Clean inside of air cleaner body.

3. Clean cover.

4. Clean and inspect element. See page 37.

5. Install clean element and cover.

6. Reset filter indicator.

If indicator shows RED shortly after installation of clean primary element, and element has been cleaned 6 to 8 times, change element.

If new primary element was used, and indicator shows RED, service secondary element.

Servicing Secondary Element:

1. Remove cover and primary element.

2. Remove secondary element.

3. Cover air inlet opening.

4. Clean inside of air cleaner body.

5. Check precleaner. Clean all parts when necessary.
6. Clean and inspect elements. See page 37.

7. Uncover air inlet opening. Install secondary element and housing. Tighten nuts to 20 ± 5 lb. ft. (2,8 ± 0,7 mkg).

8. Install primary element and cover.

9. Reset filter indicator.

Cleaning Air Cleaner Elements

Pressure Air - 100 PSI (7 kg/cm2) Maximum

1. Direct air inside element along length of pleats.

2. Direct air outside along length of pleats. Direct air inside along length of pleats.

3. Check element.

Water-40 PSI (3 kg/cm2) Maximum

1. Direct water inside element along length of pleats.

2. Direct water outside along length of pleats. Rinse element.

3. Air dry thoroughly. Check element.


1. Wash in warm water and non-sudsing household detergent.

2. Rinse with clean water (40 psi max.). See above.

3. Air dry thoroughly. Check element.

Checking Element

1. Insert light inside clean and dry element. Check and discard element if pinholes or tears are found.

2. Wrap and store good elements in a clean dry place.

Do not clean elements by bumping or tapping.

Have spare elements on hand to use while cleaning used elements.

Do not use elements with damaged pleats, gaskets or seals.

(61)Diesel Fuel System

Primary Filter Element

1. Clean element when fuel pressure gauge registers OUT with engine running.

2. Close fuel supply valves. One valve located on each side of machine, under operator's compartment.

3. Remove filter bowl and element.

4. Wash bowl and element in clean solvent.

5. Install element and bowl.

6. Open fuel supply valves.

Final Filter Element

1. If fuel pressure still registers OUT with engine running, change final fuel filter.

2. Close fuel supply valves.

3. Remove final filter with strap type wrench.

4. Clean filter base gasket surface.

5. Lubricate new filter gasket with clean diesel fuel.

6. Install new filter by hand. When gasket contacts base, tighten 1/2turn more.

7. Open supply valves and prime system. See page 39.

8. Start engine and check for fuel leaks.

Priming the Fuel System

1. Move governor control to off.

2. Open vent valve.

3. Unlock priming pump plunger.

4. Operate plunger until ...

5. ...flow of fuel from drain line is free of air bubbles.

6. Close vent valve and lock priming pump.

Fuel Tank Filler Strainer

1. Remove fuel tank filler cap.

2. Pry out strainer snap ring and remove strainer.

3. Wash strainer in clean solvent.

4. Install strainer, snap ring and cap.

(62)Cooling System

Whenever draining and refilling the cooling system, always recheck the coolant level when the engine reaches normal operating temperature. Remove cap and maintain coolant level 1/2 inch (1 cm) below the bottom of the fill pipe.

Use clean water that is low in scale forming minerals - not softened water.

Never add coolant to an overheated engine. Allow engine to cool first.

Add AVSpare Rust Inhibitors to coolant except when using permanent-type antifreeze containing rust inhibitors.

Check specific gravity of antifreeze solution frequently in cold weather to assure adequate protection.

Cleaning the Cooling System

1. Run the engine until water temperature gauge registers NORMAL. Park machine on level ground and stop engine.

2. Turn filler cap slowly to relieve pressure, then remove the cap.

3. Open radiator drain valve and drain coolant.

4. Close drain valve and fill system with cleaning solution. (1)
5. Start and run engine for 1/2hour.
6. Stop engine and drain cleaning solution.

7. Flush system with clean water until draining water is clear.

8. Close drain valve and fill system with neutralizing solution. (2)
9. Start engine and run for 10 minutes.
10. Stop engine and drain neutralizing solution.
11. Flush system with clean water.

12. Close drain valve and add coolant to proper level.

(1)2 lb. (1 kilo) Sodium Bisulphate (NaHSO4) per 10 gal (40 ltr.) water.

(2)1/2 lb. (250 g) Sodium Carbonate crystals (Na2CO3, 10 H2O, per 10 gal. (40 ltr.) water.

NOTE: Most commercial cooling system cleaners may be used.

(63)Ball And Socket Joints

1. Remove ball socket cap and shims.

2. Install ball cap without shims. Tighten bolts evenly.

3. Measure gap between socket halves. Remove cap.
4. If joints have Teflon inserts, adjust .003 to .008 inch (0,076 to 0,203 mm) tight.

Without Teflon inserts, adjust .015 to .045 inch (0,381 to 1.143 mm) loose.

Add or remove shims as necessary to obtain correct adjustment.

(64)Wheel Brakes

1. Use brake adjusting tool Part No. 5S9925.

2. Remove dust cover from front of brake backing plate.

3. Move shoe against drum. Rotate star wheel by pushing down on tool.

4. Back star wheel off 2 notches.

5. Install front dust cover plug.

6. Remove dust cover plug from rear of backing plate.

7. Move shoe against drum by pulling up on tool to rotate star wheel.

8. Back star wheel off 2 notches.
9. Install rear dust cover plug.

10. Test brakes. Check hydraulic brake fluid level. Add fluid as necessary.

(65)Parking Brake

Handle Knob

1. It should require a firm pull to snap handle over center.

2. Turn knob clockwise to tighten, counterclockwise to loosen.


1. With brake release, tighten handle knob.

2. Back knob off 4 full turns.

3. Loosen linkage clevis locknut.

4. Remove cotter pin from clevis.

5. Remove pin.

6. Remove clevis from lever. Screw clevis onto cable 4 full turns.

7. Install clevis.

8. Install pin and cotter pin.

9. Complete adjustment with handle knob.
10. Check adjustment. Lining must be free when brake is released.

NOTE: Brake is properly adjusted when it holds machine when applied, and lining is free when released.

(66)Shear Pin

1. Shear pin is in pair of flanges located in lower part of power box housing.

2. Stop engine. Remove cotter pin, loosen nut, swing cover aside. Tighten nut.

3. Remove shear pin pieces.

4. Install new shear pin.

5. Loosen cover bolt and position cover. Tighten bolt and install cotter pin.

6. Start engine and check out controls.

(67)Cutting Edge And End Bits

Cutting Edge

1. Remove cutting edge bolts.

2. Loosen end bit bolts.

3. Remove cutting edge.

4. Install new cutting edge. Use new bolts if necessary.

End Bits

1. Remove end bit bolts.

2. Remove end bit.

3. If only one edge has been used, reverse and use opposite edge.

4. Install on moldboard.

5. Narrow end bit can also be reversed and used on opposite side.

(68)Blade Lift Worm Gears

1. Adjust at one housing on each side.

2. Loosen locknut.

3. Turn adjusting screw in until it bottoms. Hold screw and tighten locknut.

(69)Blade Lift Brakes

Adjust one brake each side. Tighten adjusting nut until lining makes contact with brake block. Nut is self-locking.

(70)Flywheel Clutch

1. Maintain clutch pedal travel of 1-7/8 inches (47 mm) to 2 inches (50 mm).

2. Adjust clearance between clutch levers and release bearing thrust ring to maintain free travel.

3. Remove clutch housing inspection hole cover.

4. Remove cotter pins from adjusting nuts and screws.

5. Turn each adjusting nut in (clockwise) until levers touch thrust ring.

6. Back nut off to obtain .12 ± .02 inch (3,0 ± 0,5 mm).

7. Check clearance between levers and ring. All levers must have same clearance.

8. Check pedal free play.
9. Install cotter pins in nuts and screws.
10. Install inspection cover.