How to Replace Your Cat 305.5 Boom Cylinder

Estimated read time: 3 minutes

Find Mini Excavator Parts
Find Mini Excavator Parts

This Self-Service Options (SSO) boom cylinder job is ideal for owners who have a solid understanding of hydraulic systems and safe lifting procedures. Take your time, follow all safety notes and be sure to have the right tooling and parts ready before you begin.

While the instructions here are for the 305.5 Mini Hydraulic Excavator, you can expect installation to be similar on your Cat mini excavator model. SSOs provide detailed service instructions and recommended parts and tooling for your specific equipment. That means you can feel equipped to do the maintenance and do it correctly.

For the 305.5 boom cylinder replacement, you need:

Recommended Parts

  • Seal kit
  • Boom cylinder
  • Boom cylinder GP
  • Rod assembly

Required Tooling

  • Tooling A: Used to remove and install bearing
  • Tooling B: Used to remove and install cylinder head

Watch this video to see how the procedure is done:

   

 

 

Steps for Removing the Boom Cylinder

First, make sure the system is completely depressurized. Even after shutdown, the system can retain pressure and pose serious risks. Relieve cylinders with lock valves because they may still hold pressure after hoses are disconnected. Let the hydraulic oil cool before handling any components. Place drain pans before opening the system and follow proper containment and disposal procedures. Now:

  1. Remove the bolt and guard.
  2. Disconnect hose assemblies.
  3. Attach a lifting device to the rod end of the boom cylinder, which is about 80 pounds (36 kg).
  4. Remove the bolt and pin assembly.
  5. Lower the boom cylinder to the ground.
  6. Attach a lifting device to the boom cylinder (150 pounds or 68 kg) again.
  7. Remove clip and set hose assemblies aside.
  8. Remove bolt and pin assembly.
  9. Remove the boom cylinder completely.

How to Install the Boom Cylinder

  1. Attach a lifting device to boom cylinder.
  2. Install boom cylinder into position.
  3. Install pin assembly and bolt.
  4. Position hose assemblies and install clip.
  5. Attach lifting device to the rod end of the boom cylinder (80 pounds or 36 kg).
  6. Raise cylinder into position.
  7. Install the pin assembly and bolt.
  8. Reconnect hose assemblies.
  9. Reinstall guard and bolt.
Boom cylinder on a mini excavator
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Torque Specifications:

  • Plugs: 128 ± 6 N·m (95 ± 5 lb ft)
  • Head: 847 N·m (625 lb ft)
  • Piston: 2070 N·m (1530 lb ft)
  • Setscrew: 32 N·m (23 lb ft)

 

You're Done!

That completes the boom cylinder replacement for a Cat 305.5 Mini Hydraulic Excavator.

Find the Self-Service Options you need. Enter your equipment’s serial number to view parts and step-by-step instructions specific to your machine.

WARNING
Cylinders equipped with lock valves can stay pressurized even after hose removal. Always relieve all pressure before working on the cylinder to avoid injury or death.
NOTICE
Be prepared to catch any fluid before you disconnect hoses or disassemble components. Use proper containers and dispose of fluids properly.

 

 

 

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