Renovation of the Liebherr D926 TI-E A4 Engine in the LR 1160 Crane

Introduction

We present a comprehensive overhaul of the Liebherr D926 TI-E A4 engine carried out by the WIBAKO team in the Liebherr LR 1160 lattice crawler crane. This is a robust, all-terrain crane with high load capacity, used on construction sites for bridges, wind farms, and large industrial facilities. The D926 TI-E A4 unit is a 6-cylinder, inline diesel engine known for its high torque and durable construction, often used in Liebherr machines. The manufacturer of the machine, Liebherr, is one of the leaders in crane technology worldwide, and its own line of diesel engines is designed for demanding, continuous operation in harsh conditions.

The LR 1160 came to our service while working on a construction site in the Łódź Voivodeship, near Łódź. On-site, we diagnosed a clear loss of power and difficulties with starting after longer downtimes. Our mobile service secured the machine, performed initial measurements, and organized logistics. After preliminary diagnostics, we decided to dismantle the power unit and transport the engine to our main base in Kojszówka.

In this article, we describe the full course of work: from the first symptoms and measurement procedures, through verification and rebuilding of components, to testing on the engine dynamometer and final assembly in the machine. The whole process concludes with a section on usage recommendations after the overhaul and a list of example machines in which this type of power unit is used.

Preliminary Diagnostics in the Machine

The initial symptoms indicated wear of the cylinders and pistons and possible valve leaks: smoking under load, noticeable increased oil consumption, and a drop in compression felt in the work culture. To confirm our suspicions, we performed a sequence of field tests:

1) Measurement of compression pressure on all cylinders - uneven values and below nominal.
2) Cylinder leak-down test - increased losses indicating wear of rings and poorer valve sealing.
3) Endoscopy of the combustion chambers - visible deposits and scratches, suggesting progressive wear of the bore.
4) Exhaust gas analysis under no-load and auxiliary load conditions - confirmed smoking.

The test results justified the decision for a complete dismantling of the unit from the LR 1160 and conducting a major overhaul in WIBAKO's workshop conditions. This made it possible to carry out a thorough verification of the geometry of the parts, restore nominal assembly clearances, and perform final calibration on the dynamometer.

Dismantling the Engine from the Machine

The dismantling was carried out at the crane's work site with the assistance of a crane provided by the client. Following the procedure, we disconnected the batteries and prepared the workstation by marking hoses, conduits, and electrical bundles. We dismantled the accessory components that hindered access: intake and exhaust piping, intercooler, coolant hoses, and fuel lines. Special attention was paid to the disposal and recycling of operating fluids in accordance with environmental standards.

After unscrewing the engine mounts and disconnecting the auxiliary drive, the unit was safely removed and placed in a transport crate. Each dismantled component was labeled and packed in dedicated containers to shorten assembly time and minimize the risk of errors. The engine was transported to our headquarters in Kojszówka, where the actual overhaul work began.

Verification of Components in the Workshop

In the workshop, we conducted a complete disassembly of the D926 TI-E A4 engine. All parts underwent washing and cleaning in a closed-loop system, and then went to measurement stations. The verification confirmed the initial diagnosis - clear wear of the crankshaft-piston system and deteriorated sealing at the valve seats. We performed:

- Measurements of diameters and ovality of the cylinder sleeves and surface roughness control.
- Measurement of runout and diameters of the crankshaft journals, inspection of oil channels, and non-destructive testing.
- Verification of connecting rods: tightening, longitudinal bending, weight, and condition of bolts.
- Checking the camshaft - wear on journals and lobes, signs of improper lubrication.
- Complete verification of the cylinder head: geometry, seats and guides, leak test in a water bath under pressure.
- Verification of the turbocharger for axial and radial play and condition of the rotor and housing.

The injection system (pump and injectors) was dismantled and sent to a specialized external facility cooperating with WIBAKO for testing on a test bench and possible regeneration. Simultaneously, we collected a set of spare parts matched to the engine's serial number to restore factory parameters.

Regeneration and Repair

Crankshaft-Piston System

The sleeves were replaced, and the block was prepared according to the assembly specification. We used new pistons with a complete set of rings designed to ensure proper sealing and oil control. The crankshaft underwent grinding in a dedicated range and a thorough inspection of oil channels and centrifugal separators. We replaced the main and connecting rod bearings, and the connecting rods were balanced and brought to uniform mass parameters. We paid attention to the fit of the piston pins and the axial alignment of the piston-connecting rod sets.

Engine Head

The head was planed, guides, valves, and seals were replaced, and we performed lapping of the seats. The leak test after machining confirmed the proper operation of the valve system. Adjusting the valve clearances after assembly ensures correct timing phases and stable starting.

Fuel System

The injection pump and injectors were tested on an external test bench. The doses and injection angles were adjusted, and worn components were replaced with new or regenerated ones. We flushed the high-pressure lines and checked them for micro-cracks.

Accessories

The turbocharger, after verification, received a new set of bearings and seals. The alternator and starter were sent for regeneration, and we reviewed the electrical wires and replaced worn-out terminals. All auxiliary pumps and thermostats were checked, and components with established preventive maintenance intervals were replaced.

Professional Assembly

We assembled the engine while maintaining nominal assembly clearances and tightening procedures. We used factory torque settings and angles, and degreased and secured the mating surfaces. We applied new gaskets and O-rings, as well as brand new filters. After assembly, the engine was placed on our dynamometer.

Testing on the Engine Dynamometer

WIBAKO has its own engine dynamometer, which in the crane industry is an advantage that ensures full verification after the overhaul. We start the test from the break-in stage under controlled conditions: for a minimum of 16 operating hours, the engine runs with a light load of around 20-30% of the nominal value. During this time, we monitor parameters such as oil pressure, coolant temperature, EGT, idle stability, uniformity of cylinder operation, the amount of blow-by into the crankcase, and smoking.

After the break-in stage, we proceed to multiple full load tests. The dynamometer records torque and power curves, as well as the response to rapid load changes, which reflects the operating conditions of the LR 1160 during lifting and driving. Based on this, we verify the correctness of the assembly, the efficiency of the turbocharger, and the tightness of the intake system. The cooperating injection facility provides protocols from the pump and injector settings, which we compare with our data to confirm that the dose and injection angle are optimal for this configuration.

The dynamometer also allows for the simulation of variable loads, which helps to detect anomalies that are not visible during short tests in the machine. Thanks to complete logging of parameters, we create an engine card provided to the client: it contains graphs, limit values, and operational recommendations. Such transparency builds trust and reduces the risk of unplanned downtimes after returning the machine to work. It is worth noting that as one of the few companies in the region, we combine diesel engine service with a full dynamometer test, which speaks to the quality and predictability of the overhaul effect.

Installing the Engine in the LR 1160

After the tests were completed, the engine was prepared for reinstallation in the LR 1160. Our mobile service delivered the unit in a dedicated transport frame. We carried out the installation using a crane provided by the client. The team introduced the engine into the compartment and then precisely seated it on the mounts, checking the co-axiality of the couplings and connections with auxiliary systems. We tightened all bolts according to the manufacturer's sequences, and we verified the bayonet and pin connections for clearances.

Simultaneously, we recreated the piping and installations. We flushed the cooling system, installed new hoses and clamps, and flushed and pressure-tested the radiator and intercooler for leaks. In the intake, we used new gaskets at the joints and paid attention to the correct arrangement of conduits to eliminate the risk of abrasion. We bled the fuel system, replaced filters, and installed check valves to prevent fuel backflow after downtimes.

We reviewed the electrical installation and recreated the wiring according to the documentation. The alternator and starter, after regeneration, underwent a load test. After filling the operating fluids, we performed a control start. Together with the crane operator, we conducted a series of functional tests: from idle running, through lifting under light and medium loads, to short driving tests. At each stage, we checked operating temperatures, pressures, smoking, and the tightness of all connections. After positive verification, we prepared an assembly protocol and handed over the engine for operation.

The final step was to instruct the crew on usage after the overhaul: proper starting and cooling procedures, level checks, monitoring parameters on the panel, and responding to unusual sounds. This provided the operator and maintenance manager with clear guidelines that help maintain the engine within parameters and extend its lifespan.

Engine Maintenance After Overhaul

Every engine after overhaul at WIBAKO is covered by a warranty, as well as a service care program. We recommend the first filter change after 50 operating hours and a review of the connections between the engine and components. Subsequent inspections are planned every 250 operating hours, but no less than once every 3 months. After 50 operating hours, our service comes to the machine's work site to assess the operational condition, check for leaks, belt tensions, the condition of wires, and the accuracy of sensor readings. We also remind about regular monitoring of fuel quality and cleanliness of the intake system.

Information About Machines That Use This Engine

The Liebherr D926 TI-E A4 engine is available in various configurations in Liebherr machines. It can be found in selected models of LTM self-propelled cranes from the generational transition, medium-capacity LR crawler cranes, and some Liebherr R series crawler excavators. Example models where it can be found (depending on the year and specifications): LTM 1040/1, LTM 1055 in older versions, LR 1160, as well as selected R excavators with bucket capacities in the range of 1.3-1.8 m³. In case of doubts about compatibility, please contact us - we will verify the configuration by serial number.

Summary

The completed overhaul of the Liebherr D926 TI-E A4 diesel engine restored the LR 1160 to full functionality and factory parameters. The combination of precise verification, quality parts, and dynamometer testing guaranteed stable operation across the entire load range. The client received measurement protocols and operational recommendations. As WIBAKO, we combine experience in construction machinery service with workshop facilities, a mobile team, and our own dynamometer - this is a proven recipe for a quick return of the machine to tasks without unnecessary downtimes. We remind you of the inspection after 50 operating hours - our service will come to the site and confirm the proper operation of the entire system.