Usage:
487 (6KW),
495 (5TZ),
687 (4FZ),
695 (8MW) Tree Harvesters;
550 (7ZN),
570 (4XR),
580 (7CN) Wheel Harvesters
Description of Change: A new bypass valve is being used in order to bypass the hydraulic oil cooler when operating the machine in cold ambient temperatures. Bypassing the hydraulic oil cooler avoids overcooling the hydraulic oil.
The new bypass valve improves the operation of the hydraulic system. The old bypass valve was spring actuated. The new bypass valve contains a thermostat that maintains the hydraulic oil temperature within a narrow working temperature range regardless of the ambient temperature.
Adaptable To: The new 177-2006 Bypass Valve replaces the 166-1975 Bypass Valve (not canceled). The new bypass valve is effective with 550 (7ZN167-Up), 570 (4XR177-Up) and 580 (7CN203-Up) Wheel Harvesters. The new bypass valve is adaptable to first production for the machines listed.
Modification Procedure
1. Park the machine on a smooth, flat surface.
2. Lower all implements to the ground.
3. Engage the parking brake and stop the engine.
Right Side of the Machine Vacuum pump switch.
4. Engage the vacuum pump in order to reduce hydraulic oil loss. Moving the switch downward will engage the vacuum pump.
Left Side of the Machine Location of the hydraulic tank and hydraulic breaker relief valve.
Hydraulic Breaker Relief Valve
5. Relieve the pressure in the hydraulic tank by pressing the button on the hydraulic breaker relief valve.
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Care must be taken to ensure that fluids are contained during performance of inspection, testing, adjusting and repair of the machine. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids. Refer to Special Publication, NENG2500, "Caterpillar Tools and Shop Products Guide", for tools and supplies suitable to collect and contain fluids in Caterpillar machines. Dispose of all fluids according to local regulations and mandates.
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Left Side of the Machine (1) Bypass Valve.
Left Side of the Machine (1) Bypass Valve. (2) Hose Assembly. (3) Adapter. (4) Adapter.
6. Disconnect hose assembly (2) from adapter (3).
7. Remove adapter (3) from 166-1975 Bypass Valve (1).
8. Remove 166-1975 Bypass Valve (1) from adapter (4).
NOTE: The new 177-2006 Bypass Valve has an arrow stamped in the side of the valve body that indicates the direction of hydraulic oil flow. Make sure that after the new bypass valve is installed, the arrow is pointing upward. When the arrow is pointed upward, hydraulic oil will flow back to the hydraulic tank.
9. Install the new 177-2006 Bypass Valve (1) on to adapter (4).
10. Install adapter (3) on new 177-2006 Bypass Valve (1).
11. Connect hose assembly (2) to new 177-2006 Bypass Valve (1).
12. Disengage the vacuum pump.