Hydraulic Pressure Does Not Build Up In The Main Hydraulic Pump Caterpillar

Problem:

There may be a loose 125-8689 nozzle in the main pump regulator of the M312, M315, AND 318 Excavators. The main hydraulic pressure in a machine with a loose nozzle can no longer build pressure above 50 bar (725 psi). The affected machines appear to have lost hydraulic power.

Solution:

a. Remove plug (P1) from the destroking spool of the main pump regulator. Refer to the following illustration.

b. Check nozzle (O1) to insure that it is properly seated. Torque nozzle (O1) to 6.5 N·m (58.0 lb in). (Required Tool: 3 mm socket head wrench)

c. Install plug (P1) onto the regulator.

NOTE: Although not related to the problem in this article, also check the torque of the second nozzle (O2). Refer to the illustration.

a. Remove the short plug (P2) and remove the long plug (P3).

b. Torque second nozzle (O2) to 6.5 N·m (58.0 lb in).

c. Install both plugs (P2) and (P3).

Illustration

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