Engine Overhaul of Liebherr D9508 A7 in LTM 1500-8.1 Crane: Process and Testing on the Dynamometer

Engine Overhaul of Liebherr D9508 A7 in Mobile Crane Liebherr LTM 1500-8.1: Comprehensive Service and Testing on Engine Test Bench

Comprehensive service and rebuilding of diesel engines is our specialty, and mobile cranes Liebherr are a significant part of the machines serviced by WIBAKO in the off-highway sector. Recently, we had the opportunity to carry out a thorough engine overhaul of the carrier Liebherr D9508 A7, which is the heart of the powerful all-terrain mobile crane Liebherr LTM 1500-8.1. This technologically advanced unit's reliability is crucial for the timely execution of construction and loading projects.

The Liebherr LTM 1500-8.1 crane is one of the flagship machines in its class. It is a mobile crane with impressive lifting capacity, designed to operate in the most challenging terrain and road conditions (all-terrain). It is powered by two Liebherr engines. The carrier engine, Liebherr D9508 A7, is an 8-cylinder diesel unit with a power output of 500 kW (680 HP), driving the movement and key hydraulic systems. Meanwhile, a 6-cylinder Liebherr D936L A6 engine is responsible for the superstructure functions (rotation, lifting). The Liebherr brand, known for German precision, is synonymous with quality in construction and lifting machines.

Our mobile service was called to a client in the vicinity of Krakow, in the Małopolskie Voivodeship, due to a failure of the carrier engine. Preliminary diagnostics revealed concerning symptoms. The operator reported complete engine shutdown during standard operation, and a visual inspection indicated signs of overheating. The cause of the overhaul turned out to be overheating and seizing of the engine, suggesting serious mechanical and thermal damage.

The initial diagnostics in the field involved a visual inspection of the operating temperature indicators, checking the condition of the cooling system, and attempting to manually rotate the engine. The inability to rotate the crankshaft confirmed engine seizure, which was sufficient grounds for immediate disassembly and transport of the unit to our specialist base in Kojszówka for a complete diesel engine overhaul.

Work Stages: Professional Diesel Engine Overhaul Liebherr D9508 A7

Our comprehensive service guarantees the return of the Liebherr LTM 1500-8.1 machine to full operational capacity. Below we present detailed stages of the service, from disassembly to final tests on the engine test bench.

Engine Disassembly

The process of disassembling the engine from the Liebherr crane was carried out by our mobile service in the area of Krakow. The client, as agreed, provided a crane for the safe extraction of the powerful Liebherr D9508 A7 engine. Our mechanics began by disconnecting all auxiliary equipment, fuel, electrical, and hydraulic lines, as well as securing the connections of the cooling system and air intake. Each component is marked and cataloged, ensuring efficient and compliant with service standards later assembly. After disconnecting the diesel engine from the gearbox and mounting brackets, the unit was safely transported to our WIBAKO workshop, where verification began.

Component Verification

At the WIBAKO workshop, after initial cleaning, we proceeded with a full verification of the engine. Since the engine was seized, the process began with disassembly into parts. Washing and ongoing verification by mechanics confirmed the preliminary diagnosis – engine seizure. Inspection of the components revealed serious damage to the pistons and cylinder liners, as well as melting of the bearings due to overheating.

• Verification of the Cylinder Head: We conducted a leak test (immersion in heated water using compressed air), which revealed micro-cracks caused by thermal shock. The valve seats and clearances were also checked.
• Verification of the Crankshaft: This included a visual inspection for cracks and signs of overheating. A crankshaft runout measurement and journal measurements were performed. It was determined that crankshaft grinding was necessary due to thermal and frictional damage.
• Verification of the Connecting Rods: Measurements of twisting and longitudinal bending were taken, as well as the weight and condition of the mounting bolts.
• Verification of the Turbocharger: Testing of axial and radial clearances showed that the turbocharger requires regeneration.

Regeneration and Repair (Connecting Rod-Piston System, Cylinder Head, Fuel System, Accessories)

Our comprehensive service covered all key components of the Liebherr D9508 A7 engine:

Connecting Rod-Piston System: We replaced a complete set of new pistons, rings, cylinder liners, and crankshaft bearings (main and connecting rod). The crankshaft underwent regeneration in the form of grinding, restoring nominal geometric parameters, which is crucial for proper oil pressure and engine longevity.

Engine Cylinder Head: Due to thermal cracks, the head required regeneration. We performed planing, replaced guides and valves. A leak test after cylinder head regeneration confirmed its full functionality.

Fuel System: The injection pump and injectors were subjected to verification on a test bench, and then underwent regeneration at a specialized external facility to ensure precise fuel dosing and optimal operation after repair.

Accessories: In addition to turbocharger regeneration, we performed service on the starter, alternator, and all electro-mechanical components and sensors, ensuring that the entire diesel engine was assembled from components of the highest efficiency. All filters and operating fluids were also replaced.

Professional Engine Assembly

After regeneration and repair of all components, the professional assembly of the engine Liebherr D9508 A7 took place. This stage requires the highest precision, using dedicated torque tools. The assembly of the connecting rod-piston system (bearings, crankshaft, connecting rods, pistons) was carried out with strict tolerances. Next, the cylinder head and timing system were installed (after prior regeneration of the camshaft and replacement of worn components). It is crucial to follow the order of tightening bolts and use new seals and gaskets. Professional engine assembly guarantees its long and trouble-free operation, which is why WIBAKO pays special attention to it.

Testing on the Engine Test Bench

Having our own engine test bench is a key asset for WIBAKO, distinguishing us in the diesel engine service market. Thanks to it, we can conduct tests under controlled load conditions, even before installation in the Liebherr LTM 1500-8.1 crane. Our test bench allows for precise checking of the parameters of the Liebherr D9508 A7 engine after repair.

The test on the test bench was conducted in stages and lasted a minimum of 16 engine hours, ensuring proper bedding of new components. Initially, the diesel engine is started under light working conditions, with a load of 20-30% of nominal power. This "bedding" cycle allows for checking tightness, monitoring temperature and oil pressure, and preliminarily ruling out irregularities. After this period, if the engine maintains basic operating parameters, it is repeatedly loaded to full power to ensure it achieves nominal parameters, is dynamic, and operates smoothly under maximum load.

Every engine, including the Liebherr D9508 A7, leaves our engine test bench only with complete documentation and confirmation that its power, torque, fuel consumption, and smoke emissions are within factory norms. Only tests in controlled conditions of the test bench give WIBAKO and the client 100% certainty that the engine overhaul has been carried out comprehensively and professionally.

Engine Installation

Engine installation of Liebherr D9508 A7 in Liebherr LTM 1500-8.1, back in the area of Krakow, was carried out by our mobile service mechanics. This process is as meticulous as disassembly and repair. It involves installing the unit in the compartment while adhering to service standards and using new washers, bolts, and fasteners.

Our team pays great attention to accurately connecting all lines, connectors, sensors, and accessories. This includes precise installation of engine mounts, couplings, and electrical connections, as well as piping for the intake and cooling systems. The machine is then prepared for the first start-up, which always includes replacing filters, thoroughly bleeding the systems (fuel, cooling), and preliminary testing of the systems. Additionally, we check the tightness of all newly connected components and replace air piping if necessary to eliminate potential failures. Thorough tests are performed during the first start-up in the presence of the machine operator. After positive tests regarding the proper operation of the diesel engine, absence of leaks, and full functionality, an assembly protocol is signed.

Engine Maintenance After Overhaul and Information About Machines with Liebherr D9508 A7 Engine

Every engine that leaves WIBAKO service is covered by a warranty, and we provide full service support after repair. For the Liebherr D9508 A7, we recommend the first critical filter change (oil, fuel) and checking of accessory connections after 50 engine hours of operation from start-up. This is a key inspection during which our mobile service mechanics check the overall condition of the accessories, monitor proper operation, and verify that no leaks have occurred during normal operation. We recommend subsequent technical inspections every 250 engine hours, but no less frequently than every 3 months.

The Liebherr D9508 A7 engine is a high-power unit that, besides being used in all-terrain mobile cranes Liebherr LTM 1500-8.1, can also be found in other large construction and lifting machines from Liebherr requiring high power, such as some material handling excavators, larger models of wheeled loaders, or self-propelled cranes from the LTM series. WIBAKO provides service for all these off-highway machines.

Summary and Benefits for the Client

The comprehensive overhaul of the Liebherr D9508 A7 diesel engine in the Liebherr LTM 1500-8.1 crane is an investment that restores the construction machine to its full power and reliability. WIBAKO, as a service specialized in diesel engine service for Liebherr and other brands, guarantees the highest quality of work performed. Our professional approach, supported by advanced diagnostics and the ability to test engines on our own engine test bench, minimizes the risk of failure and reduces downtime.

The benefits for the client are tangible: long engine life, optimal fuel and oil consumption, and the assurance that the crane is fully ready to tackle the most challenging tasks. We emphasize that a key element of comprehensive service is also service support after 50 engine hours – this is the moment when our mobile service will visit the client again in the Małopolskie Voivodeship (or another location) to conduct the first critical inspection.

Places for Internal Links:

If you need construction machinery service, see which brands of off-highway machines we service. Our mobile service is at your disposal throughout Poland, including in the vicinity of Katowice, Łódź, and Opole. In the WIBAKO offer, you will also find detailed information about our engine test bench and load testing.