Low or Erratic Hydraulic Power is Experienced on Certain Wheeled Excavators{5455} Caterpillar

Excavator:

M322D (S/N: W2S1-UP)

M322D (S/N: W2T1-UP)

Introduction

The problem that is identified below does not have a known permanent solution. Until a permanent solution is known, use the solution that is identified below.

Problem

Caterpillar has received reports of low hydraulic power or erratic hydraulic power complaints on M322D and M322D MH wheel-type excavators and wheel-type material handlers. This loss of hydraulic power in certain instances has been caused by a failed 276-0155 Pump Control Valve Gp that is installed on the 273-1405 Pump Control Valve Gp . Parts that have been returned to this date have indicated a failed upper flange of the 254-2034 Seat (9) in the valve body. The location of the failure is called out in the following Illustration 1.

Solution

Caterpillar is investigating the root cause of these failures, and more information is needed to better understand the cause of these failures. If a field report of low hydraulic power or erratic hydraulic power has been received, perform the following steps in order to resolve the issue.

Note: The 273-1405 Pump Control Valve Gp controller breaks down into the serviced components for the 276-0155 Pump Control Valve Gp that can be found in Table 1.

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Illustration 1	g01595314
276-0155 Pump Control Valve Gp

1. Measure the pressure at the load sensing signal limiter and record the pressure at the load sensing signal limiter and the pressure at the main pump according to instructions that are documented in Testing and Adjusting, RENR9465.

2. If the main pump or the pressure at the load sensing signal limiter is out of the required specification, perform the following procedure in order to verify that the plug is loose.

   1. Check the torque of the plug (13) by placing a mark on the plug and housing.

   2. Set the torque wrench to 40 N·m (30 lb ft).

   3. Turn plug (13) with the torque wrench until the wrench "clicks".

   4. Check the position of the mark.

   5. If the mark moved, the plug (13) was loose.

   6. Torque plug (13) to 100 N·m (74 lb ft), and recheck pressures.

3. If the pressure check is still out of the required specification or erratic, perform the following procedure in order to verify that the plug is loose.

   1. Remove the 6E-5060 Cap As .

   2. Check the torque of the sealing locknut (1) by placing a mark on the nut and plug (13) .

   3. Set a torque wrench to 14 N·m (124 lb in).

   4. Turn plug (13) with the torque wrench until the wrench "clicks".

   5. Check the position of the mark.

   6. If the mark moved, locknut (1) was loose.

   7. Torque locknut (1) to 22 N·m (16 lb ft) and recheck pressures.

4. If plug (13) and locknut (1) were not adjusted, attempt to perform a main pump calibration by using ET.

5. If the procedure for calibrating the main pump calibration fails, remove the 276-0155 Pump Control Valve Gp that is from the main pump controller.

6. Inspect the valve for broken internal components, or damages to the surface of the piston.

7. Open a DSN ticket in order to communicate with Caterpillar if torquing of the plug resolved the issue or if torquing the locknut resolved the issue or if a component inside the 276-0155 Pump Control Valve Gp failed.

8. Document the information and attach pictures to the DSN of the part number of the failed hardware and the part number that was ordered in order to resolve the failure.

A final fix will be communicated when the root cause is identified, and the issue is resolved.