Repair of the Cummins QSB6.7 Engine in the LiuGong 848H Wheel Loader

Engine overhaul of Cummins QSB6.7 (129 kW) in LiuGong 848H wheel loader

The LiuGong 848H wheel loader is a modern and efficient machine designed for intensive loading, unloading, and earthworks. This model is widely used in gravel mines, industrial plants, sorting facilities, and large construction sites. It is powered by a six-cylinder Cummins QSB6.7 diesel engine with an output of 129 kW, known for its good power-to-fuel consumption ratio and high operational culture.

A client from the Małopolskie Voivodeship, near Krakow, approached our WIBAKO service with a LiuGong 848H wheel loader that began to show symptoms of power loss, increased engine oil consumption, and noticeable smoking under load. The machine was operating continuously while loading bulk materials, which, due to high mileage, led to natural wear of the power unit. After preliminary diagnostics, a decision was made to carry out a comprehensive overhaul of the Cummins QSB6.7 engine.

Preliminary diagnostics of the Cummins QSB6.7 engine in the LiuGong 848H wheel loader

The first stage of work was the preliminary diagnostics of the engine directly in the machine. Our mechanics conducted a compression pressure measurement, which showed significant differences between individual cylinders. Additionally, increased oil consumption and blue smoke during load operation were observed. An endoscopy of the cylinders was also performed, confirming wear on the sleeve surfaces and traces of piston operation under reduced lubrication conditions.

Based on the collected data, the Cummins QSB6.7 engine was classified for a major overhaul. The disassembly of the power unit was planned at the machine's work site, using a crane provided by the client.

Disassembly of the engine from the LiuGong 848H wheel loader

The disassembly of the Cummins QSB6.7 engine was carried out by our mobile service directly at the client's location. The work began with disconnecting the electrical system, fuel system, and components of the intake and exhaust systems. Next, the cooling system hoses and all sensitive equipment components were secured to avoid damage during the removal of the power unit.

The engine was removed from the frame of the LiuGong 848H wheel loader using a crane and appropriate slings. After disassembly, the engine was prepared for transport and transported to our headquarters in Kojszówka, where a detailed verification was initiated under workshop conditions.

Verification of the Cummins QSB6.7 engine in the WIBAKO workshop

After delivering the engine to the workshop, a complete disassembly was performed. All components were thoroughly cleaned and subjected to technical assessment. The verification confirmed advanced wear of the cylinders and pistons, which was the direct cause of compression loss and increased oil consumption.

Additionally, the crankshaft was checked, showing signs of wear on the journals; however, after measuring runout and diameters, it was classified for regeneration through grinding. The engine head was sent for a leak test in a water bath and inspection of the valve seats.

Repair process of the Cummins QSB6.7 engine

Crankshaft and piston system

As part of the repair of the crankshaft and piston system, the crankshaft was regenerated through precise grinding of the journals and installation of new main and connecting rod bearings. New cylinder sleeves, pistons, and piston rings compliant with Cummins specifications were used. Each connecting rod was checked for geometry, weight, and condition of the bolts.

Engine head

The regeneration of the head included surfacing the mating surface, replacing valve guides, valves, and checking for leaks after assembly. The head was prepared for further operation in accordance with the standards of the Cummins engine manufacturer.

Fuel system

The fuel system of the Cummins QSB6.7 engine underwent comprehensive verification. The injectors were tested on a test bench, and the injection pump was sent to an external specialized regeneration facility. After the return of the components, they were recalibrated.

Engine accessories

The turbocharger was checked for longitudinal and transverse play. The alternator and starter underwent electrical and mechanical inspection. All seals and consumable parts were replaced.

Professional assembly of the engine

The assembly of the Cummins QSB6.7 engine was carried out according to the manufacturer's technical documentation. Each stage of assembly was controlled in terms of tightening torques, assembly clearances, and cleanliness. The engine was prepared for stand testing.

Test on the engine dynamometer

One of the key stages of the overhaul was the test of the Cummins QSB6.7 engine on our engine dynamometer. As one of the few companies in Poland, we have a dynamometer that allows testing diesel engines before their installation in construction machines. The engine operated for a minimum of 16 hours under partial load and was then repeatedly loaded to nominal values.

During the tests, oil pressure, operating temperatures, combustion parameters, and stability under load were monitored. The dynamometer test allows for the elimination of the risk of failures after installation and provides the client with a real guarantee of the quality of the repair performed.

Installation of the engine in the LiuGong 848H wheel loader

After positive tests on the dynamometer, the engine was transported to the client. The installation was performed using a crane, adhering to full service procedures. New air intake hoses were installed, the cooling system's tightness was checked, and filters and oil were replaced.

After starting the engine, operational tests were conducted in the presence of the machine operator. After confirming proper operation and the absence of leaks, an installation protocol was prepared.

Engine maintenance after overhaul and summary

After the overhaul, the Cummins QSB6.7 engine in the LiuGong 848H wheel loader regained full efficiency, power, and correct operating parameters. The client received recommendations for the first inspection after 50 hours of operation, which will be carried out by our mobile service. Subsequent inspections are recommended every 250 hours or no less than every 3 months.

WIBAKO specializes in comprehensive service of construction machines and overhaul of diesel engines of brands such as Cummins, Deutz, Liebherr, Perkins, and Volvo. With our technical background and engine dynamometer, we ensure the highest quality of services and safety in the operation of machines.