D400E Series II Articulated Truck Steering, Suspension, and Ejector Body Hydraulic Systems Caterpillar

Signal and Pressure Reducing Valve (Steering) - Check

Usage:

The signal and pressure reducing valve is used to improve the steering response. An unusual response of the steering system could be caused by a plugged orifice in the signal and pressure reducing valve.

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NOTICE

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.

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Illustration 1	g00838977
Location of the signal and pressure reducing valve

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Illustration 2	g00621630
The signal and pressure reducing valve is located to the right of the transmission in front of the ejector control valve. The access panels have been removed for photographic clarity. (1) Signal and pressure reducing valve (2) Pilot pressure port (3) Tank port

Park on a level surface. Engage the parking brake. Stop the engine and make sure that the pressure in the hydraulic system is zero.

Install the steering frame locks. Refer to Operation and Maintenance Manual, SEBU7379, "Steering Frame Lock".

Remove the line to the pilot pressure port (2) and remove the fitting at the pilot pressure port (2). The fitting has an orifice that should be checked for blockage. This will expose the valve spool. Remove the valve spool and observe the two orifices in the valve spool. There is one orifice in each end of the valve spool.

Check the orifices in the valve spool for blockage. Check the screen for blockage. You must remove the orifices from the spool in order to check the screen. The screen is inside of the spool. Each orifice is secured with Loctite. Loctite is a retaining compound. Also check for any contamination in signal and pressure reducing valve (1). If contamination is present, you have two choices: You can clean the signal and pressure reducing valve or you can replace the signal and pressure reducing valve. Refer to Disassembly and Assembly, SENR9145, "Signal and Pressure Reducing Valve (Steering) - Remove and Install".