LOCK AS-CYLINDER 6V5551 - Caterpillar

At operating temperature, the hydraulic oil tank is hot and under pressure.Hot oil and components can cause personal injury. Do not allow hot oil or components to contact skin.Before installation or removal of any hydraulic test equipment, relieve the pressure in the hydraulic tank by slowly loosening the filler cap.
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, "Caterpillar Tools and Shop Products Guide" for tools and supplies suitable to collect and contain fluids on Caterpillar products.Dispose of all fluids according to local regulations and mandates.
Do not turn the steering wheel when the engine is running and a low pressure gauge has been installed in the steering circuit. If the steering wheel is turned, the pressure of the oil to the steering cylinders will be too high for a low pressure gauge.
Table 1
Required Tools    
Tool    Part Number    Description    Quantity    
A     198-4240     Digital Pressure Indicator     1    
Move the machine to a level, hard surface. Shut off the engine and engage the parking brake.
Illustration 1 g00928778
Rear of 621 and 627 Wheel Tractor-Scrapers (1) Test port for the steering pump for the 621 and 627 Wheel Tractor-Scrapers
Illustration 2 g01125051
Rear of 623 Wheel Tractor-Scraper (1) Test port for the steering pump for the 623 Wheel Tractor-Scraper
Remove the dust cap from test port (1) of the steering pump. Connect Tooling (A) to test port (1) .
Illustration 3 g00931173
Right Side of the Steering Control Valve, Underneath Operator Compartment (2) Test port for the outlet of the steering control valve
Remove the dust cap from test port (2) of the steering control valve. Connect Tooling (A) to test port (2) .
Start the engine and operate the engine at HIGH IDLE. Raise the bowl and release the brakes.
Turn the machine toward the left until the left turn stops hit. Continue steering to the left. Take the readings from both of the pressure gauges. Subtract the reading at the steering control valve from the reading at the steering pump. The difference should read 15500 520 kPa (2250 75 psi).
Illustration 4 g00929707
Section view of steering control valve (3) Steering control valve (4) Nut (5) Retainer
If the pressure reading is out of tolerance, stop the machine and shut off the engine. Loosen nut (4) and adjust retainer (5) in order to change the steering system pressure. Turn the retainer clockwise in order to increase the steering system pressure. Turn the retainer counterclockwise in order to decrease the steering system pressure. Refer to Specifications, "Steering Control Valve" for more information on the pressure change of the retainer.
Repeat Step 4 through Step 6 until the steering system pressure is correct. Refer to Specifications, "Steering Control Valve" for the appropriate torque.
Start the engine and operate the engine at high idle. Raise the bowl and release the brakes.
Turn the machine