BELT-SERPENTINE 3637389 - Caterpillar

Illustration 1 g01331327
Cab (1) Joystick (stick and swing) (2) Joystick (boom and bucket)
Illustration 2 g01527986
Main control valve (top view) (3) Stick I control valve (4) Swing control valve (5) Left travel control valve (6) Right travel control valve (7) Boom I control valve (8) Attachment control valve (9) Bucket control valve (10) Boom II control valve (11) Stick II control valveWhen joystick (1) and/or joystick (2) are operated, the pilot control valves send pilot pump oil through the pilot lines to pilot ports at the main control valve in order to shift the spools in the main control valve. Pilot oil that enters the control valves from the top causes the machine operations in Table 1. Pilot oil that enters the control valves from the bottom causes the machine operations in Table 2.
Table 1
Pilot line     Control Valve     Machine Operation    
(3)     Stick I control valve     STICK OUT    
(4)     Swing control valve     SWING RIGHT    
(5)     Left travel control valve     FORWARD LEFT TRAVEL    
(6)     Right travel control valve     FORWARD RIGHT TRAVEL    
(7)     Boom I control valve     BOOM RAISE    
(9)     Bucket control valve     BUCKET CLOSE    
(10)     Boom II control valve     BOOM RAISE    
(11)     Stick II control valve     STICK OUT    
Table 2
Pilot line     Control Valve     Machine Operation    
(3)     Stick I control valve     STICK IN    
(4)     Swing control valve     SWING LEFT    
(5)     Left travel control valve     REVERSE LEFT TRAVEL    
(6)     Right travel control valve     REVERSE RIGHT TRAVEL    
(7)     Boom I control valve     BOOM LOWER    
(9)     Bucket control valve     BUCKET OPEN    
(10)     Boom II control valve     BOOM LOWER    
(11)     Stick II control valve     STICK IN    
Illustration 3 g01528065
Pilot control valve (stick and swing) (1) Joystick (2) Rod (3) Return passage (4) Passage (5) Spool (6) Plate (7) Rod (8) Spring (9) Seat (10) Seat (11) Spring (12) Spring (13) Return chamber (14) Return passage (15) Passage (16) Spool (17) Port (return pressure to valve) (18) Passage (pilot supply pressure) (19) Port (reduced pressure to valve) (20) Port (pilot supply) (21) Port (tank)When joystick (1) is moved to the right, plate (6) tilts to the right. Plate (6) pushes down on rod (7). Seat (10) moves down against the force of metering spring (11) and spring (12). The force of metering spring (11) shifts spool (16) downward. Passage (15) opens. The pilot oil flows through passage (20), passage (18), passage (15) and port (19) to the main control valve. The pilot oil pressure shifts the spool of the main control valve. This enables the implement operation or swing operation.The return pilot oil at the opposite end of the spool in the main control valve returns to the pilot control valve through port (17). Since rod (2) is not pushed down by