Deploying the New Fleet of Caterpillar D11T Dozers Amid Mixed Expectations

[MikePhua]

The D11T and Its Role in Modern Mining
The Caterpillar D11T is one of the most powerful track-type tractors ever built, designed for high-production mining, heavy dozing, and ripping operations. Introduced as an evolution of the D11R, the D11T features a Cat C32 ACERT engine producing up to 850 horsepower, paired with an electronically controlled powertrain and modular components for easier serviceability. With an operating weight exceeding 230,000 pounds, the D11T is engineered to move massive volumes of material efficiently and reliably.
Caterpillar, founded in 1925, has sold thousands of D11-class dozers globally, with the D11T becoming a staple in coal, copper, and iron ore mines. Its popularity stems from its ability to withstand extreme duty cycles, often running 20–22 hours per day in remote locations.
A Yard Full of Giants and Uncertain Destinations
In early 2013, a fleet of 21 brand-new D11Ts was spotted at Hastings Deering’s yard in Brisbane, Australia. The sight of so many machines lined up sparked speculation about their destination. Some believed they were awaiting delivery to large-scale mining operations, while others suspected they were cancelled orders due to a downturn in commodity demand.
Terminology annotation:

• Stock Machines: Equipment held by dealers for immediate sale, often staged in yards for customer inspection.
  
• Cancelled Orders: Units manufactured but not delivered due to changes in buyer demand or project delays.
  
• Hastings Deering: One of Caterpillar’s largest dealers in the Asia-Pacific region, responsible for assembly, distribution, and support.
  

The presence of these machines reflected both Caterpillar’s production momentum and the volatility of the mining sector. In previous years, similar yards had been filled with 994 wheel loaders and 793 haul trucks awaiting buyers—a sign of aggressive inventory positioning.
Operator Experience and Reliability Challenges
While the D11T is often described as a dream machine from the operator’s seat, not all experiences have been flawless. One operator reported persistent overheating and exhaust system failures across three units running in Indiana. Despite operating in cold conditions, the machines struggled with thermal management, especially during continuous operation.
The issue was traced to a bellows component in the exhaust system, designed to redirect gases for reburn—a precursor to full Tier 4 emissions compliance. The bellows failed repeatedly, requiring cylinder head replacements and causing downtime.
Recommendations for exhaust system reliability:

• Inspect bellows for cracks or fatigue every 500 hours
  
• Monitor exhaust backpressure and temperature sensors
  
• Replace EGR components proactively in high-duty cycles
  
• Use OEM gaskets and torque specs during head replacement
  

Tier 3.5 Emissions and EGR Complexity
The D11T units in question were equipped with what technicians referred to as “Tier 3.5” configurations—engines that incorporated partial emissions control features without full Tier 4 compliance. This included exhaust gas recirculation (EGR) systems and rudimentary aftertreatment components.
While designed to reduce NOx emissions, these systems introduced complexity and potential failure points. The EGR cooler, responsible for lowering the temperature of recirculated gases, was often cited as a weak link. If clogged or leaking, it could lead to intake contamination and reduced combustion efficiency.
Suggestions for EGR system management:

• Flush EGR coolers during major service intervals
  
• Cap off bellows and bypass EGR after warranty expiration (where legal)
  
• Monitor intake manifold cleanliness and turbocharger performance
  
• Train onsite mechanics in emissions system diagnostics
  

Deployment in High-Duty Mining Operations
The D11Ts were reportedly destined for sites like Bear Run Mine in Indiana, operated by Peabody Energy. These mines run equipment nearly continuously, with dozers logging over 150 hours per week. Under such conditions, even minor design flaws can escalate into chronic issues.
Despite the challenges, operators praised the cab comfort, visibility, and control layout of the D11T. From the glass in, the machine offered a refined experience—air suspension seats, intuitive joysticks, and climate control systems that made long shifts more bearable.
Conclusion
The arrival of 21 new D11Ts in Brisbane marked both a celebration of Caterpillar’s engineering prowess and a reflection of the mining industry’s unpredictability. While the machines promise unmatched pushing power and operator comfort, their emissions systems and thermal management require vigilant maintenance. As Tier 4 regulations continue to shape engine design, the D11T stands at the crossroads of brute force and environmental compliance—challenging operators and mechanics to adapt, innovate, and keep these giants moving.