CONTROL-UNIT 4319471 - Caterpillar

Illustration 1 g02556240
(1) 193-7879 Boot
Drain rubber boot (1) on the actuator linkage periodically.The maximum amount of leaking oil that is acceptable and the corresponding amount of time for the accumulation of the oil follows:
Approximately 10 mL (0.34 oz) per 60 hours of operation
Approximately 100 mL (3.4 oz) per 600 hours of operation
Approximately 990 mL (33.7 oz) per 6000 hours of operationAdjustments for the Hydraulic Oil Pressure
To operate properly, the electrohydraulic actuators require correct oil pressure. If the pressure is insufficient, the engine will not start. If the pressure is excessive, the hydraulic system can be damaged. Two adjustments can be made for the hydraulic oil pressure:
The hydraulic lines have a pressure relief valve that regulates the hydraulic system's pressure. This pressure relief valve is adjusted to achieve sufficient pressure for start-up and for normal operation. If the pressure becomes excessive, the valve diverts the oil back to the pump.
The hydraulic oil pump has a pressure relief valve that is a backup to the pressure relief valve in the hydraulic lines. If the pressure becomes excessive, the pump circulates the oil internally.Adjustment of the Pressure Relief Valve for the Hydraulic Lines
Table 1
Required Tools Qty
8T-0855 Pressure Gauge 1
Illustration 2 g03781005
Left side view (In-line engine)
(1) Adjusting bolt
(2) Locknut
(3) Pressure relief valve
(4) Plug
Illustration 3 g03781006
Left side view (Vee engine)
(1) Adjusting bolt
(2) Locknut
(3) Pressure relief valve
(4) Plug
Remove plug (4) from the manifold. Attach the 8T-0855 Pressure Gauge onto the opening for the plug.
Run the engine at rated speed. Loosen locknut (2) on the bottom of pressure relief valve (3). Use an allen wrench to turn adjusting bolt (1) to obtain a pressure of 1550 35 kPa (225 5 psi).Note: Sometimes, the pressure must be increased to avoid the generation of diagnostic codes during start-up. This is due to restarting an engine that has a low viscosity of hydraulic oil because the oil is hot. If this occurs, the pressure can be increased to a maximum of 1725 kPa (250 psi).
Tighten locknut (2).
Stop the engine.
Remove the pressure gauge. Install plug (4) into the manifold.Adjustment of the Pressure Relief Valve for the Hydraulic Oil Pump
Normally, the hydraulic oil pump's pressure relief valve is unlikely to require adjustment. Use the following procedure if the pump is serviced.
Illustration 4 g03781008
(1) Cap
(2) Locknut
(3) Adjusting screw (not shown)
Remove cap (1) to gain access to adjusting screw (3) (not shown). Loosen locknut (2).
Turn adjusting screw (3) fully inward. Then, turn the adjusting screw outward for two and one-half turns.
Tighten locknut (2) and install cap (1).Hydraulic Actuator System Oil Recommendations
Caterpillar recommends the use of Cat® Hydraulic Oil in the Hydrax System.Caterpillar offers two hydraulic oil products:
Cat® HYDO Advanced 10
Cat® Bio HYDO AdvancedCat HYDO Advanced 10
Cat HYDO Advanced 10 fully replaced Cat® HYDO oil. Cat HYDO is no longer available.Cat HYDO Advanced 10 is preferred in most hydraulic systems and in most hydrostatic systems when ambient temperature is between −20° C to 40° C (−4° F to 104° F).If a different viscosity is required due to ambient temperatures, the following Cat oils