In the world of construction machinery, few sights are as recognizable as the powerful Caterpillar bulldozer.
The Cat D6N model, weighing nearly 20 tons, is a machine used on construction sites and in earthworks around the world. Its heart is the Caterpillar C6.6 engine – a six-cylinder unit with a capacity of 6.6 liters, featuring a Common Rail system and an output of approximately 111 kW. Although durable, it also requires a major overhaul from time to time.
Initial symptoms and engine disassembly
The bulldozer arrived at our workshop with suspected serious engine failure. After preliminary inspections, we decided to disassemble it. We began the process by:
- disconnecting the electrical system and draining the operating fluids,
- removing the covers, mufflers, filters, and wiring harnesses,
- dismantling the radiators and components of the front assembly of the machine.
Machines of this class often operate in harsh conditions, resulting in significant contamination of the unit. In this case, the dirt was particularly intense.
Removing and verifying the engine
After disconnecting it from the transmission and securing all the hoses, we successfully removed the engine. It was then taken to the workshop, where it was thoroughly cleaned and disassembled into its component parts. During the verification, we checked, among other things, the condition of the pistons, cylinder head, and timing system. Even at this stage, many defects not visible during daily operation could be identified.
Repair process – step by step
The overhaul of the Caterpillar C6.6 engine included a full range of work:
- processing the crankshaft and replacing the bearings,
- installing the pistons and connecting rods while adhering to the appropriate torque specifications,
- renewing the cylinder head – machining, replacing valves, and checking for leaks,
- installing the turbocharger, fuel system, and timing system,
- replacing the oil pump, gaskets, and oil pan.
Each component was thoroughly cleaned and lubricated before assembly, and the piston rings were set according to the manufacturer's guidelines.
Installation in the machine and additional work
After completing the overhaul and testing on the dynamometer, the engine was returned to the bulldozer. During the installation, we also performed additional service work:
- sealing the steering cylinders and replacing the hydraulic hoses,
- regenerating the blade and replacing the plow hoses,
- replacing all filters and operating fluids – from engine oil, through oils in the final drives and transmission, to hydraulic fluid and cabin filters.
Final result
The engine was started and tested under full load. The operating parameters matched the standard values, and the machine was returned to the client fully operational and ready for many more years of work.
The entire video can be seen here.
