Engine overhaul of Cummins QSB4.5 (Tier 3) in LiuGong 6520E pneumatic roller

The LiuGong 6520E pneumatic roller is a modern machine used in road construction, designed for compacting asphalt surfaces and related mixtures. Equipped with a Cummins QSB4.5 (Tier 3) engine, valued for its high work economy and durability, it is a popular choice among construction companies operating in the Małopolska region. Our WIBAKO service received the machine that was working on a large road investment near Krakow. The operator reported a drop in power, uneven operation of the unit, and noticeable smoking under load.

The Cummins QSB4.5 engine is a four-cylinder design with high durability, commonly used in rollers, loaders, and off-highway machines. The manufacturer, Cummins Inc., is one of the global leaders in the field of diesel engines. In this case, we performed a full diagnosis and a comprehensive overhaul of the unit at our headquarters in Kojszówka.

Preliminary diagnostics in the machine

After reporting the fault, our mobile service went to the investment site. During the initial tests, we noticed that the engine had problems with smoothly reaching RPM, generated excessive vibrations, and showed increased oil consumption. The suspected cause, which was to be confirmed, was the wear of the cylinders and pistons resulting in a drop in compression.

As part of the diagnostics, we conducted a compression pressure measurement, a cylinder leak test, and an endoscopic examination of the combustion chamber. The parameters were clearly below the manufacturer's standards, confirming the need for disassembly of the unit and transport to our base.

Disassembly of the engine from the LiuGong 6520E roller

We disassembled the Cummins QSB4.5 engine on-site, using a crane provided by the client. As part of the standard procedure, we disconnected the cooling system, removed the air hoses, fuel system, and accessory components. All connections were cleaned and properly secured against contamination. After unscrewing the engine mounts and preparing the machine for unloading, the unit was safely removed and transported to our headquarters in Kojszówka.

Verification of the engine in the workshop

After disassembling the engine into parts, we confirmed significant wear of the cylinders and pistons. The sleeves had visible pitting, and the piston rings were heavily worn, which explained the low compression level. The condition of the connecting rods was assessed as borderline, and the crankshaft required full measurement and regeneration. The cylinder head underwent a leak test in a water bath and revealed leaks in two valve seats that required machining.

Repair and regeneration process

Connecting rod and piston system

As part of the work, we performed:
- grinding of the crankshaft,
- replacement of connecting rod and main bearings,
- replacement of cylinder sleeves,
- installation of new pistons and rings,
- verification and regeneration of connecting rods (straightening, weight control).

Cylinder head

The cylinder head underwent full regeneration: planning, replacement of valve guides, installation of new valves, and a complete leak test. This allowed us to restore the factory operating parameters.

Fuel system

The injection pump was sent to a specialized facility for regeneration. The injectors were placed on a test bench, where the appropriate opening pressure was set. The supply pump and high-pressure hoses were replaced.

Engine accessories

The turbocharger was regenerated, and the starter and alternator were verified for proper operation. The coolant pump, belts, and guide rollers were also replaced.

Test on the engine dynamometer

One of the greatest advantages of WIBAKO service is our own engine dynamometer, which allows for full testing of combustion units under load conditions. After assembling the Cummins QSB4.5, we conducted over 16 hours of start-up testing under light working conditions (20-30 percent load). This allowed us to check the tightness of the systems, stability of parameters, and any micro-leaks.

After the initial phase, we began multiple full load tests, analyzing temperature, oil pressure, stability of RPM, and power generated by the engine. The dynamometer allows us to recreate working conditions very close to the actual load of the pneumatic roller. Each stage of the tests ended positively, and the unit's parameters were within the factory values of Cummins.

Installation of the engine in the machine

We reinstalled the engine in the LiuGong 6520E roller on-site, traveling with our mobile service to the Krakow area. The process included positioning the unit in the frame, mounting the engine mounts, connecting the fuel system, electrical system, oil return lines, and intake and cooling hoses. We performed a complete replacement of filters and necessary fluids.

After installation, we conducted start-up tests in the presence of the operator. We checked the tightness of all connections, stability of RPM under mechanical load, and the engine's response to dynamic changes in power demand. The final stage was the preparation of the installation protocol.

We recommended the first service inspection after 50 operating hours, including filter replacement, connection checks, and re-verification of accessories.

Machines using the Cummins QSB4.5 engine

This engine is used in:
- LiuGong series 8 loaders,
- LiuGong 6520E and 6611 road rollers,
- Case and New Holland machines,
- some Manitou and Terex machines.

Summary

The comprehensive overhaul of the Cummins QSB4.5 (Tier 3) engine in the LiuGong 6520E pneumatic roller restored the full functionality of the unit and ensured its long and stable operation. The work performed, tests on the dynamometer, and professional installation guarantee that the machine can return to intensive work on the construction site. After about 50 operating hours, we recommend the first warranty inspection by WIBAKO service.