4729899 Excavator Butter Pump Repair Kit for EX1900-6 EX2600 EX3600 EX5600 

Part number 4729899 is a Hitachi original grease pump repair/seal kit, also known as a grease pump repair/seal kit. It does not belong to the category of "power components", but rather a consumable package that restores the sealing and pressure building capabilities of existing butter pumps. It usually corresponds to an independent butter pump (manual/pneumatic/electric centralized lubrication pump) installed near the side wall/counterweight of the cab, at the interface between the pump head or body and the one-way valve block. Because the lubrication pump brands (such as BEKA, LINCOLN, or Hitachi made pumps) and pump head versions of Hitachi models from different eras are different, the 4729899 in the public catalog will not be used interchangeably across models; The safest approach when purchasing is to send the old pump nameplate photo (brand/model/serial number)+old bag label photo (4729899)+complete machine model and serial number to the merchant for verification, to avoid buying sealing sections or O-ring specifications that are similar in appearance but incompatible.
 

This set is essentially a collection of vulnerable seals for the pump head: commonly including main seals (cups or U-cups) for pistons/plungers, guide rings, buffers, end cap O-rings, lip seals, small valve cores/spring washers for check valves (inlet and outlet), and sealing gaskets/copper pads between the pump body and valve block. Nitrile/polyurethane or fluororubber resistant to NLGI 2 grease will be used on the material, and low compression permanent deformation is required to maintain pressure for a long time under frequent reciprocating (or pneumatic pulse). Its value lies not in "increasing pressure", but in blocking internal control leaks: once the main seal ages and becomes hard, cuts edges, or flips lips, the pump will "look like it is oiling but cannot apply pressure/reach the far end", and replacing the entire pump is often more economical than replacing the correct specification of the sealing package first.

It has only one core principle: follow the "disassembly and maintenance of pump head" and do not forcefully tighten or randomly push screws on the outside. The typical rhythm is: stop the machine → release pressure and empty/isolate the pump chamber → remove the pump head end cover → take out the piston assembly → take photos to record the direction/stacking sequence (many people install it incorrectly) → replace all seals in the package, clean the valve seat and throttle hole (be careful not to push impurities into the main pipeline) → reinstall according to the specified order/torque → re exhaust (make several more strokes until there are no bubbles in the grease discharge continuously) and perform a simple inspection of "blocking the outlet to check the pressure/observing the grease discharge from the far end".