Lift Cylinder Piston May Crack and Seize on Certain 993K and 993K2 Large Wheel Loaders {5102} Caterpillar

Wheel Loader

993K (S/N: LWA1-UP; Z4D1-UP; Z9K1-UP; Z4Z1-UP)

Reference: Refer to Specifications, KENR5565, "993K Wheel Loader Machine Systems" , Lift Cylinder section for serial number prefixes Z4D and Z4Z.

Reference: Refer to Specifications, KENR5826, "993K Wheel Loader Electrohydraulic System" , Lift Cylinder section for serial number prefixes LWA and Z9K.

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.

Problem

The lift cylinder piston may crack and seize on products listed above. This failure may result in downtime and repair.

Solution

Illustration 1	g06220017
View of failed piston removed from cylinder group

Illustration 2	g06220814
View of 247-4930 Piston with 3.0 mm (0.11 inch) undercut radius features. (A) Radius 3.0 mm (0.12 inch) (B) 6.6 ± 1.0 mm (0.26 ± 0.04 inch)

Caterpillar is aware of this problem, but an interim solution has not been identified.

In case of failure, replace the failed 247-4930 Piston with new piston of same part number.

Note: Use only 247-4930 Piston with 3.0 mm (0.12 inch) undercut radius features.