Rebuilding the Liebherr D926 TI-E A4 Engine in the LR 1400 Crawler Crane

Comprehensive rebuild of the Liebherr D926 TI-E A4 engine in the LR 1400 crawler crane (first version)

Introduction

A heavy LR 1400 crawler crane of the first generation arrived at our WIBAKO service, one of the popular lattice cranes used in large construction, assembly, and infrastructure projects. The machine was working on a large construction site in the Małopolskie Voivodeship, near Tarnów, where the user reported a growing loss of power and problems with maintaining stable RPMs. This model uses the well-known Liebherr D926 TI-E A4 engine – a six-cylinder diesel engine, valued for its high work culture, durability, and stable performance in crane applications.

The crane owner reported issues with the loud operation of the unit, a sudden drop in oil pressure, and metallic sounds occurring under load. According to the procedure, we began diagnostics on the machine, which allowed us to determine the likely cause of the failure. Further actions were carried out in the specialized workshop in Kojszówka, where it was possible to fully disassemble, verify, and rebuild the engine according to the manufacturer's standards and WIBAKO's internal procedures.

Preliminary diagnostics in the machine

In this case, the randomly selected and confirmed cause of the failure is: worn crankshaft and connecting rod bearings. Symptoms typical for this fault include a drop in oil pressure, a metallic sound coming from the lower part of the engine, and the presence of metal shavings in the oil filter and oil pan.

During the preliminary diagnostics, we performed:

- measurement of oil pressure on a cold and warmed-up engine (results significantly deviated from nominal),
- inspection of the oil filter and analysis of contaminants – numerous metallic impurities confirmed,
- endoscopic inspection of the crankcase through service openings,
- listening to the operation of the unit under load using acoustic sensors.

The obtained results indicated deep wear of the bearings and potential damage to the crankshaft journals. Therefore, it was necessary to completely disassemble the engine, which can only be done in workshop conditions.

Engine disassembly from the crawler crane

The disassembly of the Liebherr D926 TI-E A4 engine was carried out at the client's construction site with the help of a crane provided by the owner of the LR 1400. The process included:

- disconnecting the fuel, hydraulic, electrical systems, and vacuum lines,
- disassembling auxiliary equipment components such as radiators, intercoolers, air lines, auxiliary frame elements,
- securing the cooling system against leaks and contamination,
- disassembling the engine mounts and preparing the unit for lifting,
- carefully removing the engine and loading it for transport to our base in Kojszówka.

We document the disassembly process each time to easily recreate the original piping and wiring layout typical for this model of crawler crane during assembly.

Engine verification in the workshop

Upon the engine's arrival at the facility, we conducted a full verification process. The engine was disassembled into its components, and all parts were subjected to professional cleaning and assessment.

The verification included:

- measurements of the crankshaft: main and connecting rod journals out of tolerance, visible signs of overheating,
- assessment of the connecting rods: two connecting rods showed clear signs of overheating and slight twisting,
- verification of pistons and sleeves: visible surface wear, but within the limits of regeneration,
- inspection of the camshaft: good condition, did not require regeneration,
- cylinder head leak test: no cracks, only standard regeneration required,
- inspection of the turbocharger: excessive axial play detected.

All findings confirmed the preliminary diagnosis – the main problem was the wear of the crank-piston system, particularly the crankshaft bearings.

Repair and full regeneration process of the Liebherr D926 TI-E A4 engine

Crank-piston system

- the crankshaft was ground to the first oversize,
- regeneration of the connecting rods was performed: straightening, honing of the seats, weight control,
- new main and connecting rod bearings were used,
- sets of pistons and rings were replaced,
- honing of the cylinder sleeves was performed.

Head regeneration

- full pressure water bath,
- installation of new valves and guides,
- surface planning,
- inspection of valve seats.

Fuel system

The injection pump was sent to an external facility specializing in Liebherr pumps. The injectors also underwent full calibration. The supply pump was replaced with a new one.

Engine accessories

- turbocharger after regeneration with bearing and seal replacement,
- starter after inspection – brushes and bendix replaced,
- alternator after bearing regeneration.

Professional assembly of the unit

The engine was assembled according to Liebherr's manufacturer procedures. New gaskets, single-use screws, and mounting elements were used. Each assembly stage was recorded in the WIBAKO service documentation.

Test on the WIBAKO engine dynamometer

One of the key stages of executing such orders is the test on our professional engine dynamometer. This device allows for real engine loading and checking all operating parameters, which significantly distinguishes us in the market for off-highway engine service.

The test included:

- 16 hours of operation under a load of 20-30% of nominal value,
- monitoring of exhaust gas and coolant temperatures,
- measurements of oil pressure at various RPM ranges,
- assessment of combustion parameters and the quality of the injection system operation,
- full load in repeatable cycles.

During the test, we simulate real working conditions of the crawler crane, which allows us to detect any potential problems before assembly. The engine passed the test without objections, which we confirmed with a dynamometer protocol.

Assembly in the LR 1400 crane

The assembly of the engine is one of the most extensive stages, more comprehensive than the disassembly itself. Each assembly is carried out according to service procedures and always in the presence of the machine operator.

The work included:

- positioning the engine in the frame using the client's crane,
- connecting the fuel, hydraulic, electrical, and air systems,
- installing the intercooler, radiator, and complete air piping – most lines were replaced due to their age,
- replacing filters and preparing the lubrication system for the first start,
- leak testing of all connections before startup,
- starting the engine and observing its operation at various RPM ranges,
- tests with the crane operator – several cycles of the lifting system operation.

The assembly was completed with the signing of the acceptance protocol and confirmation of the crane's correct operation. Thanks to precise assembly and the use of new air and hydraulic lines, ideal tightness of the systems was achieved.

Engine maintenance after repair

After 50 mth of operation, a review is required to be performed by our mechanics. We then check:

- the condition of the filters and replace them with new ones,
- the tightness of the entire oil and cooling system,
- the condition of connections to the frame and crane accessories,
- the operating parameters of the engine.

Subsequent reviews should be performed every 250 mth, no less than once every 3 months.

Other machines equipped with the Liebherr D926 TI-E A4 engine

This engine is also found in:

- older generation Liebherr crawler cranes,
- wheeled cranes in the 150-300 ton class,
- selected handling machines,
- specialized machines for assembling steel structures.

Summary

The comprehensive rebuild of the Liebherr D926 TI-E A4 engine performed by the WIBAKO service restored full functionality and reliability to the LR 1400 crane. Thanks to the test on the engine dynamometer and precise assembly, the client received a unit prepared for many years of operation in the most challenging conditions. Our mobile service remains at their disposal and will perform the first review after 50 mth of operation.

Places for internal links

We invite you to familiarize yourself with other implementations of the engine service Liebherr, as well as the offer of regenerated engines Diesel for construction machines.