Renovation of the Liebherr D9508 A7 Engine in the LTM 1500-8.1 Crane

Engine overhaul Liebherr D9508 A7 (500 kW) in the mobile all-terrain crane LTM 1500-8.1

The mobile crane (all-terrain) Liebherr LTM 1500-8.1 is one of the most advanced designs in the large self-propelled crane segment. This machine is commonly used in the implementation of the most demanding assembly projects in energy, heavy industry, infrastructure construction, and steel structure assembly. Its reliable operation is ensured by a powerful diesel engine Liebherr D9508 A7 with a rated power of 500 kW, which provides appropriate operating parameters both during travel and during lifting operations.

A crane LTM 1500-8.1 arrived at our service with symptoms of gradual power loss and increased engine oil consumption. The machine had been working intensively on investments in the Katowice area, where our mobile construction machinery service performed preliminary diagnostics and prepared the crane for the disassembly of the power unit. The engine was then transported to our headquarters in Kojszówka, where we conducted a comprehensive overhaul of the Liebherr diesel engine.

Liebherr, as a manufacturer of both machines and combustion engines, designs its units with long service life and high operational culture in mind. The D9508 A7 engine is an eight-cylinder unit with a large displacement, designed to operate under high loads for many hours. Despite its robust construction, high mileage and harsh operating conditions necessitated a complete overhaul and regeneration of the engine.

Preliminary diagnostics of the engine in the machine

The reason for the decision to overhaul was wear of the cylinders and pistons, manifested by a drop in compression, noticeable smoking, and increasing engine oil consumption. During the preliminary diagnostics performed in the machine, our mechanics measured the compression pressure, analyzed the engine's operating parameters from the diagnostic computer, and inspected the intake and exhaust systems.

In the next stage, targeted diagnostics were performed, including an endoscopic assessment of the condition of the cylinders and a leak test of the oil system. The results unequivocally confirmed significant wear of the crank-piston assembly, qualifying the Liebherr D9508 A7 engine for a complete major overhaul.

Disassembly of the engine from the LTM 1500-8.1 crane

The engine disassembly was carried out by our mobile service at the client's site. According to the manufacturer's procedures, the engine was removed using a crane provided by the client. Before starting the operation, all accessory components, electrical installations, cooling system, and air intake were disconnected. Special attention was paid to properly securing the fuel and oil lines.

After unscrewing the mounting brackets and preparing the lifting points, the engine was safely removed from the crane frame and prepared for transport. The entire disassembly process was carried out in accordance with service standards, which helped avoid additional damage and reduce machine downtime.

Verification of the Liebherr D9508 A7 engine in the workshop

Upon delivery of the engine to our workshop, we began a detailed verification of the unit. The process included complete disassembly of the engine into its basic components, cleaning all parts, and conducting a thorough inspection. The crankshaft, connecting rods, pistons, cylinder liners, bearings, and timing system components were verified.

Significant wear of the cylinder liners and piston rings was confirmed, as well as signs of operation at the limits of permissible parameters. Additionally, the cylinder heads were checked for leaks and wear of the valve seats.

Repair and regeneration process of the engine

Crank-piston system

As part of the overhaul, the crank-piston system was regenerated. The crankshaft underwent measurement and grinding processes, new main and connecting rod bearings were selected, and the connecting rods were verified for geometry and strength. New pistons, rings, and cylinder liners were used, in accordance with the specifications of the manufacturer Liebherr.

Engine head

Each of the heads was subjected to a leak test in a heated water bath. Surface planning, replacement of guides and valves, and precise lapping were performed. This restored full functionality to the timing system and combustion chamber.

Fuel system and accessories

The fuel system of the Liebherr D9508 A7 engine was thoroughly checked. The injectors underwent testing on a test bench, and the fuel pump was verified for efficiency. The turbochargers were inspected for play and leaks. Additionally, the starter and alternator were regenerated.

Professional assembly of the engine

After completing all regeneration work, the engine was assembled according to the manufacturer's technical documentation. Each stage of assembly was monitored by experienced mechanics, and all tightening moments were carried out using torque tools.

Engine test on the engine dynamometer

One of the key stages of the overhaul was the test on the engine dynamometer. As one of the few companies in Poland, we have a dynamometer that allows testing large diesel engines used in construction machinery and self-propelled cranes. The Liebherr D9508 A7 engine operated on the dynamometer for several hours under controlled load conditions.

Initially, the engine operated at a load of 20-30 percent of its rated power, which allowed for proper breaking in of the components. The load was then gradually increased to full working parameters. Oil pressure, temperatures, combustion parameters, and stability of operation were monitored. The tests confirmed the full functionality of the engine and its readiness for reassembly in the machine.

Installation of the engine in the mobile crane

The installation of the Liebherr D9508 A7 engine in the LTM 1500-8.1 crane was again carried out at the client's location. The process included precise seating of the engine in the machine frame, connecting all installations, and replacing components of the air and cooling system piping. After assembly, detailed leak tests were performed, and the engine was started for the first time in the presence of the operator.

After positive tests, an assembly protocol was prepared, and the crane was approved for further operation.

Summary and post-repair service

The comprehensive overhaul of the Liebherr D9508 A7 engine restored the full functionality of the LTM 1500-8.1 mobile crane. The client gained a reliable power unit with a warranty and assurance of further safe operation. According to recommendations, the first service inspection will be carried out after 50 operating hours of the engine by our mobile service.

We provide comprehensive service for Liebherr diesel engines, repairs and regeneration of power units, and service for self-propelled cranes throughout Poland.