Repair of the Liebherr D9508 Engine in the LTM 11200-9.1 Crane

Engine overhaul Liebherr D9508 in Liebherr LTM 11200-9.1 mobile crane

Introduction

The mobile crane Liebherr LTM 11200-9.1 is one of the largest and most technologically advanced self-propelled cranes in the world. It stands out with its impressive lifting capacity, high precision of operation, and the ability to extend the telescopic boom to record lengths. The drive of this powerful structure is provided by the Liebherr D9508 A7 engine with a power of 505 kW, while the superstructure unit is Liebherr D936L A6. Both units work together in the drive system, ensuring smooth and safe operation.

Our WIBAKO service received the crane showing symptoms of power loss, uneven engine operation, and excessive oil consumption. After initial diagnostics, it was confirmed that both engines – the carrier (D9508) and the superstructure drive (D936L A6) – required overhauling. The work was carried out at our headquarters in Kojszówka, after the engines were disassembled by our mobile service in the vicinity of Katowice.

Engine disassembly

The disassembly of the Liebherr D9508 engine from the LTM 11200-9.1 mobile crane was carried out using a auxiliary crane provided by the client. Our team ensured the proper disconnection of all fuel, hydraulic, and electrical lines, as well as securing the cooling and air intake systems. Each stage of disassembly was documented to facilitate the assembly process after the overhaul. The engines were properly secured and transported to our workshop in Kojszówka, where a full verification began.

Verification of components

The verification revealed significant wear of the cylinders and pistons, confirming earlier suspicions regarding compression loss. Detailed measurements of the crankshaft, connecting rods, and valve seats were also taken. The D9508 engine showed signs of overheating on two cylinders, while the D936L A6 unit required valve replacement and head regeneration. All components were thoroughly cleaned and checked for cracks and wear according to Liebherr's standards.

Regeneration and repair

The overhaul process included complete regeneration of the crank-piston system – the cylinder liners were replaced, and the crankshaft was ground. Pistons, rings, bearings, and all seals were replaced. The engine heads underwent full regeneration: planing, replacement of valve guides, valves, and springs. The fuel system – injection pumps and injectors – was tested on a testing stand. Additionally, turbines, alternators, and starters were tested and regenerated.

Engine assembly

After completing the workshop work, both engines were prepared for installation in the Liebherr LTM 11200-9.1 crane. The assembly was carried out in accordance with all manufacturer service standards. Our team replaced the complete set of filters, fuel and air lines, and checked the tightness of the cooling and air intake systems. After assembly, the first start-up was performed with the participation of the machine operator – the engine achieved full operating parameters without any irregularities. After the tests were completed, an assembly protocol was signed.

Engine test on the dynamometer

Each engine after overhaul at WIBAKO undergoes a mandatory test on the dynamometer. This is one of the key stages of our work that distinguishes our service from other companies. The dynamometer allows checking the actual operating parameters of the engine under load conditions similar to those in the machine. The Liebherr D9508 engine was started on the test stand, where it worked for 16 hours under light load conditions (20-30% of nominal power), after which it underwent full test cycles up to 100% load. The stability of oil pressure, operating temperatures, and response to load changes were checked. The test ended positively – the engine achieved factory power parameters of 505 kW.

A similar process was undergone by the Liebherr D936L A6 engine powering the crane's superstructure. Both engines were approved for installation and allowed for further operation with full service warranty.

Engine maintenance after overhaul

After receiving the machine, the client received full service documentation and recommendations for operation. We recommend the first filter change and connection check after 50 operating hours, which is performed by our WIBAKO mobile service. Subsequent inspections are scheduled every 250 operating hours, no less than every 3 months. Through regular maintenance, we ensure long and trouble-free operation of the Liebherr D9508 engine and the D936L A6 unit.

Liebherr D9508 and D936L A6 engines – application

These engines are used in many self-propelled cranes and Liebherr construction machines – including models LTM 1450, LTM 1500, and LTM 1750. They are modern, eight-cylinder (D9508) and six-cylinder (D936L A6) diesel units, known for their exceptional durability and high power-to-weight ratio. Thanks to precise fuel injection technology and solid construction, these engines perform excellently under heavy load.

Summary

The overhaul of the Liebherr D9508 engine in the Liebherr LTM 11200-9.1 mobile crane allowed for the full restoration of the machine's efficiency. The regeneration work performed, tests on the dynamometer, and precise assembly guarantee reliability and long service life of the engine. Thanks to a comprehensive approach and modern technical facilities, WIBAKO remains one of the leaders in the industry in terms of Liebherr diesel engine service and construction machine repairs. We invite you to contact us if you need diagnostics, overhaul, or purchase of Liebherr drive units.