Repair of the Cummins QSB6.7 Engine in the Terex RT 670 Crane

Engine overhaul of Cummins QSB6.7 (168 kW) in Terex RT 670 rough terrain crane

Introduction

The rough terrain crane Terex RT 670 is a versatile machine with a lifting capacity of 70 tons, designed for operation in challenging terrain conditions. This machine, valued for its stability and mobility, is often used in infrastructure construction, steel structure assembly, and service work on construction sites. The crane is powered by a Cummins QSB6.7 engine with a power output of 168 kW, which is characterized by high operational culture, durability, and good fuel economy.

A crane that had been working in the vicinity of Katowice (Silesian Voivodeship) arrived at our WIBAKO service. The client reported issues with uneven engine operation and increased oil consumption. After initial diagnostics, it was determined that a comprehensive overhaul of the Cummins QSB6.7 power unit would be necessary.

Preliminary diagnostics

Upon the arrival of our mobile service to the client, a compression pressure measurement was performed in the cylinders, along with an oil analysis. The results indicated wear of the cylinders and pistons – the pressure in two cylinders was significantly below the norm, and metal shavings were found in the oil filter. Additionally, a bluish smoke was coming from the exhaust system, confirming the wear of the piston rings.

After confirming the diagnosis, it was decided to dismantle the engine and transport it to our facility in Kojszówka, where a full verification and overhaul of the unit was carried out.

Engine disassembly

The disassembly of the Cummins QSB6.7 engine from the Terex RT 670 crane was carried out using a crane provided by the client. Our technicians disassembled the accessory components, hydraulic hoses, cooling system, and air intake. All connections were properly secured, and the engine was placed in a transport frame and transported to the WIBAKO service facility.

Component verification

After disassembling the engine into parts, a comprehensive verification was conducted. The crankshaft was measured, connecting rods were checked, and cylinder liners and pistons were examined. The results confirmed earlier suspicions – the wear of the cylinder bores exceeded permissible values, and the piston rings were significantly worn. The verification of the cylinder head revealed minor valve leaks that required resurfacing and replacement of guides and seals.

Additionally, the injection pump was checked on the test bench, and the turbocharger was subjected to clearance checks and balancing. All components meeting tolerance standards were reused after regeneration.

Regeneration and repair

The scope of the overhaul included: honing of cylinder liners, installation of new pistons, rings, and bearings, grinding of the crankshaft, and full regeneration of the cylinder head. The fuel system was refreshed through calibration of the injection pump and injector testing. The turbocharger underwent regeneration with the replacement of bearings and seals. All components were assembled according to Cummins service standards.

After assembly, the engine was sealed, painted, and prepared for testing on the engine dynamometer.

Engine dynamometer test

WIBAKO, as one of the few companies in Poland, has an engine dynamometer that allows for testing power units before their installation in the machine. The Cummins QSB6.7 engine was started on the dynamometer after the overhaul, where it operated under load for over 16 hours at 20 to 30% of nominal capacity. After preliminary tests, the tightness, oil pressure, and operating temperature were checked. The engine was then loaded to full power of 168 kW several times to confirm its stability and performance.

The test was successful – the engine operated smoothly, without smoking or loss of power. The measurement results confirmed compliance with the factory parameters of Cummins. Thanks to the dynamometer, we can guarantee that every unit leaving our workshop is fully operational and ready for installation.

Engine installation

After the successful test, the engine was transported back to the work site of the crane in Katowice. The installation was carried out with the highest standards – all fuel hoses, air hoses, and cooling piping were replaced. After installing the unit, the torque of the bolts, the tightness of the connections, and the operation of the starting and charging systems were checked. After starting the engine, tests were conducted in the presence of the machine operator. The Terex RT 670 crane regained full functionality – the engine operated smoothly, without disturbing noises or leaks.

After the tests were completed, an installation protocol was signed, and the client received detailed documentation of the repair process and dynamometer measurements.

Engine maintenance after overhaul

WIBAKO recommends conducting the first inspection after 50 operating hours of the engine. This includes changing filters, checking connections, verifying oil pressure, and making any necessary adjustments to bolt connections. Subsequent service inspections should be performed every 250 operating hours or every 3 months. Our mobile service offers warranty and post-warranty service for Cummins engines throughout Poland.

Application of the Cummins QSB6.7 engine

The Cummins QSB6.7 engine is a popular unit used in many construction and industrial machines – from excavators and loaders to rough terrain cranes and handling machines. It can be found in models such as Terex RT 555, Grove RT540E, JCB JS330, and Keestrack R3. Due to its reliability and ease of maintenance, it is a preferred choice among heavy equipment manufacturers worldwide.

Summary

The overhaul of the Cummins QSB6.7 engine in the Terex RT 670 rough terrain crane allowed for the restoration of the machine to full functionality and efficiency. Thanks to professional service, thorough verification, and dynamometer tests, the client can be assured that their equipment will operate reliably for thousands of operating hours to come. Our experience, technical background, and knowledge of Cummins engines make WIBAKO a leader in diesel engine and construction machinery service.

We invite you to contact us regarding repairs and overhauls of Cummins engines – we provide comprehensive service, dynamometer tests, and mobile service throughout Poland.