Clearing Blocked Pivot Bearings on a CAT 279D Skid Steer

[MikePhua]

The CAT 279D and Its Suspension Design
The Caterpillar 279D is a compact track loader (CTL) engineered for high performance in rough terrain. Introduced as part of CAT’s D-series lineup, it features a suspended undercarriage system designed to absorb shock and improve traction. Each side of the track frame is supported by pivot bearings—front and rear—that allow the suspension arms to articulate. These bearings are critical to maintaining smooth ride quality and structural integrity under load.
Unlike rigid frame skid steers, the 279D’s suspension system relies on daily lubrication to prevent wear and contamination. The pivot bearings are equipped with grease fittings (zerks), but when neglected, these fittings can become clogged with hardened grease, dirt, or rust, preventing proper lubrication and leading to premature bearing failure.
Symptoms of Blocked Grease Passages
Operators may notice that the rear pivot bearings on one or both sides refuse to accept grease, even under pressure. This is often due to:

• Hardened grease obstructing the internal passage
  
• Dirt or debris packed into the fitting
  
• Damaged or faulty zerk fittings
  
• Misalignment of the grease port due to frame flex
  

Terminology:

• Zerk fitting: A small valve that allows grease to be injected into a bearing or bushing
  
• Pivot bearing: A rotating or oscillating bearing that supports movement between structural components
  
• Track frame: The assembly that supports the tracks and connects to the loader’s main chassis
  

Manual Cleaning Techniques
The first step in restoring grease flow is to remove the zerk fitting and inspect it. If the fitting itself is clogged, it can be cleaned or replaced. If the passage beyond the fitting is blocked, several manual methods may help:

• Insert a small drill bit by hand into the grease port to dislodge hardened material
  
• Use pliers to rotate the bit gently, avoiding damage to the port walls
  
• Reinstall a clean zerk and attempt to grease again
  

If the blockage persists, the track frame may need to be removed to access the bearing directly. This is a labor-intensive process but may be necessary if the bearing is completely dry or contaminated.
Alternative Clearing Methods
Several field-tested techniques have proven effective in clearing stubborn grease passages:
Oil injection:

• Fill a grease gun with penetrating oil (e.g., Blaster or 10W hydraulic oil)
  
• Remove the zerk and connect the hose directly to the port
  
• Tap the grease gun with a mallet to force oil into the passage
  
• Repeat until oil emerges from the bearing, then follow with grease
  

Kroil soak method:

• Replace the zerk with a short pipe nipple and coupler
  
• Fill the coupler with Kroil penetrating oil daily
  
• Seal with a plug and allow the oil to soak over time
  
• Once the oil breaks through, reinstall the zerk and grease normally
  

Some operators report success after several weeks of soaking, especially in cases where the grease has hardened into a waxy plug.
Preventative Maintenance and Greasing Protocol
The most effective way to avoid bearing blockage is consistent greasing. For machines like the 279D operating in dusty or muddy environments, daily greasing is essential—even if the machine is used for only a few hours.
Best practices:

• Grease pivot bearings at the end of each shift to purge contaminants
  
• Use high-quality lithium-based grease with anti-wear additives
  
• Inspect zerks weekly and replace any that show signs of damage
  
• Keep grease guns clean and store them in sealed containers
  

One retired quarry mechanic emphasized that daily greasing prevented 90% of bearing failures in his fleet. He preferred greasing at shutdown to push out moisture and debris before overnight cooling hardened contaminants.
When to Disassemble the Track Frame
If all clearing methods fail, the track frame must be removed to access the pivot bearing directly. This involves:

• Jacking up the machine and securing it safely
  
• Disconnecting the suspension arms and hydraulic lines
  
• Sliding the track frame out to expose the bearing housing
  
• Drilling out the grease port or replacing the bearing entirely
  

This procedure should be done in a clean shop environment with proper lifting equipment. Attempting it in the field without adequate support can be dangerous and may damage the frame.
Conclusion
Blocked pivot bearings on a CAT 279D are more than a nuisance—they’re a warning sign of neglected lubrication and potential mechanical failure. With a combination of manual cleaning, oil injection, and patient soaking, most blockages can be cleared without disassembly. But the real solution lies in prevention: daily greasing, clean fittings, and a disciplined maintenance routine. In compact track loaders, the smallest passage can make the biggest difference—and keeping it clear is the key to keeping the machine moving.