A 2020 Liebherr LH35 material handler with 8,900 operating hours on the clock. This is not a repair after a failure but the opposite. The owner knew that on these machines the hydraulic pumps usually need an overhaul at around 10,000 hours, so instead of waiting for an expensive failure and downtime, he ordered preventive service.

Pumps after a preventive overhaul

We had removed the main pump and the slewing pump beforehand. There was nothing wrong inside, but – as always at this mileage – we replaced the bearings and the full seal kit, and the pumps were tested on our dyno. On site we fitted the coupling, installed the main pump and the travel pump (A4), connected the pressure, pilot and suction lines and finally bled the system.

Hydraulic oil: 3,000 or 6,000 hours?

The oil in the machine had never been changed – it was black and worn out. The recommendation is simple:

every 3,000 hours – if the oil is not tested,
up to 6,000 hours – if a sample is sent for analysis once a year and the result is good.

Here it was almost 9,000 hours without a change. We cleaned the tank, filled new genuine Liebherr oil, replaced the hydraulic filter and pilot filter, and the air filter too. As old oil remains in the cylinders, control valve and travel circuit, we also connected a filtration unit to filter the whole system.

Engine: oil, fuel filters and breather

After repositioning the machine we drained the engine oil and replaced the filters. The old filters were so seized that a chain wrench was needed – at the previous change someone had not lubricated the seals. Hence a simple rule: always oil the filter seal. We also replaced:

fuel filters with water separator – a sensor alerts the operator when water collects in the bowl,
crankcase breather filter – if neglected, crankcase pressure rises, which can cause crankshaft seals to leak.

Pressure checks

After filtration we checked the working pressures: approx. 350–351 bar – exactly to spec. The pump was not damaged; it was removed in time so the machine can confidently work another ~10,000 hours.

Takeaways

A preventive pump bearing change before the typical failure mileage is much cheaper than an overhaul after the pump disintegrates and the whole system has to be cleaned.
Hydraulic oil change interval: 3,000 hours without analysis, up to 6,000 hours with an annual oil test.
Small things matter: an oiled filter seal and a regularly changed breather filter prevent trouble.

See: hydraulic pump and motor repairs, hydraulic oil filtration, construction machinery service.

Watch the repair video: 8,900 Hours and the Decision That Saved the Machine | Liebherr LH35