16740-ZY3-A01 Honda REGULATOR ASSY., PRESSURE (Honda Code 8008534).

Personal injury or death can result from sudden machine movement.Sudden movement of the machine can cause injury to persons on or near the machine.To prevent injury or death, make sure that the area around the machine is clear of personnel and obstructions before operating the machine.
Coolant System
Pressurized system: Hot coolant can cause serious burn. To open cap, stop engine, wait until radiator is cool. Then loosen cap slowly to relieve the pressure.
To relieve the pressure from the coolant system, turn off the machine. Allow the cooling system pressure cap to cool. Remove the cooling system pressure cap slowly to relieve pressure.Hydraulic System
The release of hydraulic pressure in a hydraulic circuit is required before service is performed to that hydraulic circuit. Release the pressure in the following hydraulic circuits before any hydraulic lines are disconnected or removed from that hydraulic circuit.
Boom hydraulic circuit
Stick hydraulic circuit
Bucket hydraulic circuit
Swing hydraulic circuit
Travel hydraulic circuit
Attachment hydraulic circuits (if equipped)
Pilot hydraulic circuit
Return hydraulic circuitNote: Refer to the Disassembly and Assembly Manual for additional information concerning service of the components of specific hydraulic circuits.Release of Hydraulic Pressure from the Main Hydraulic System
Personal injury can result from hydraulic oil pressure and hot oil.Hydraulic oil pressure can remain in the hydraulic system after the engine has been stopped. Serious injury can be caused if this pressure is not released before any service is done on the hydraulic system.Make sure all of the work tools have been lowered to the ground, and the oil is cool before removing any components or lines. Remove the oil filler cap only when the engine is stopped, and the filler cap is cool enough to touch with your bare hand.
Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting, and repair of the product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids.Refer to Special Publication, NENG2500, "Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Cat® products.Dispose of all fluids according to local regulations and mandates.
Perform the following steps to release the hydraulic system pressure from the main hydraulic system.Note: For additional safety, wrap hydraulic joint with material that could absorb/reduce any residual pressure of oil when released. Loosen the joint slowly, pause, and carefully check hydraulic joint for tensions indicating presence of pressure or spring force in lines or components.
Position the machine on level ground.
Illustration 1 g06185115
Fully retract the stick cylinder rod. Adjust the position of the bucket so that the bucket is parallel to the ground. Lower the boom until the work tool is flat on the ground. Refer to Illustration 1.
Release the system pressure from the implement and swing hydraulic circuits.Note: Perform Step 3.b through Step 3.d immediately after the engine is shut off to insure adequate pilot system pressure is available to release the pressure in the hydraulic circuits.
Shut off the engine.
Turn the engine start switch to the ON position without starting the engine.
Place the hydraulic activation control lever in the UNLOCKED position.
Illustration 2 g06184822
Move both joysticks in a circular motion to the FULL STROKE positions multiple times until the pilot accumulator has been exhausted.Note: Pilot pressure is required to relieve hydraulic system pressure.
Place the hydraulic activation control lever in the LOCKED position.
Start the engine to recharge the pilot accumulator.Note: Do not activate any controls when recharging the pilot accumulator.
Shut off the engine.
Repeat Step 3.b through Step 3.g until the high-pressure lines have been released.Note: Each time the accumulator is recharged, start the joysticks at different positions or rotate in the reverse direction. Doing so will ensure that the same circuit is not being relieved each time.Note: You can also move only the joysticks or pedals of the hydraulic circuit that requires service to the full stroke positions after moving joysticks in a circular motion multiple times. This action will release the high pressure only in that single hydraulic circuit. This action will also release any pressure that might be present in the pilot hydraulic circuit.
Release hydraulic system pressure in the attachment circuits.
Start the engine to charge pilot accumulator.
Shut off the engine.Note: Perform Step 4.c through Step 4.e immediately after the engine is shut off to insure adequate pilot system pressure is available to release the pressure in the hydraulic circuits.
Turn the engine start switch to the ON position without starting the engine.
Place the hydraulic activation control lever in the UNLOCKED position.
Activate the switch or pedal for the attachment circuit.
Place the hydraulic activation control lever in the LOCKED position.
Start the engine to recharge pilot accumulator.Note: Do not activate any controls when recharging pilot accumulator.
Shut off the engine.
Repeat Step 4.c through Step 4.f for each attachment circuit.
After releasing the hydraulic pressure in each of the desired hydraulic circuits, place the hydraulic activation control lever in the LOCKED position.
Turn the engine start switch to the OFF position.
Illustration 3 g06184990
Hydraulic oil tank filler cap
(A) LOCK position
(B) PRESSURE RELEASE - START position
(C) PRESSURE RELEASE - END position
(D) OPEN position
Release the pressure that may be present in the return hydraulic circuit with the following procedure. Refer to Illustration 3 for filler cap positions.
Turn the filler cap counterclockwise and move the arrow from position (A) to position (B).
Release the pressure for a minimum of 45 seconds by moving the arrow from position (B) to position (C).
Push down the filler cap and move the arrow from position (C) to position (D).Note: The travel hydraulic circuit is open to the hydraulic tank. Pressure from the travel circuit is released by releasing pressure from the return circuit.
Release the pressure that may be present in the boom