Hägglunds motor repair – overhaul and certified testing

TFS repairs and overhauls Hägglunds radial piston hydraulic motors — CA, CB, CBM, Compact, Atom, Marathon and Viking series — at its own workshop in Battipaglia, Italy: complete disassembly, dimensional inspection of every component, genuine spare parts and test bench testing before the motor is returned. As a Hägglunds partner, TFS works to the manufacturer’s specifications across the whole high-torque, low-speed range, serving customers throughout Europe and the Mediterranean.

Why Hägglunds motors call for specific expertise

Hägglunds motors are radial piston hydraulic motors with direct drive: they deliver very high torque at low speed without a gearbox, and mount straight onto the shaft of the driven machine. Their architecture — pistons arranged radially, rotating distributor, cam ring, large bearings — has nothing in common with that of a pump or an axial piston motor.

That means dedicated disassembly, measurement and testing procedures, and very tight fitting tolerances. An overhaul carried out without the manufacturer’s specifications can hand back a motor that runs but delivers less, runs hot and wears quickly: the defect is invisible at reassembly and shows up a few hundred operating hours later.

The Hägglunds series we overhaul

TFS works on the entire Hägglunds range, from the legacy series still widely installed to the current generations:

• CA and CAb series — compact direct-drive motors, widely used in marine, earthmoving and process applications.
• CB, CBm and CBp series — high torque for heavy industrial duty: mills, crushers, extruders, conveyors, winches.
• Viking series (MA and MB) — high displacement for extreme loads. These are the largest motors in the range: a Viking MB84 weighs around 1,500 kg and delivers 538 Nm of torque for every bar of differential pressure.
• Atom — the new compact generation, with high torque density.
• Marathon and Compact — integrated drives for installations with space constraints.
• Hägglunds Drive and Infinity systems — complete motor, power unit and control packages, which we also service on the hydraulic power unit side.

If the motor you need overhauled is not in these series, or comes from another manufacturer, the job is still possible: TFS is a multi-brand workshop and also works on Bosch Rexroth, Kawasaki, Casappa, Parker and Denison Calzoni.

The most common failures and what causes them

On radial piston motors the symptoms that reach the workshop are almost always these, and each points to a family of causes to be checked during disassembly:

• Abnormal noise and vibration — excessive clearance between pistons and cam ring, worn bearings, damaged distributor.
• Overheating — internal leakage dissipating energy as heat, often together with a drop in efficiency.
• Loss of torque or speed — reduced volumetric efficiency caused by wear on the internal sealing surfaces.
• Oil leaks from the seals — hardened or scored shaft seals, often the consequence of prolonged overheating.
• Oil contamination — ISO 4406 class out of specification: this is the root cause of most premature wear. In these cases we also work on the circuit, with filtration and fluid conditioning.

It is worth saying that not all wear is a failure. On a motor that has run for years within certified tolerances, surface wear is normal: the overhaul serves to bring it back within specification before it turns into unplanned downtime.

Cavitation on Hägglunds motors: how to recognise it and what causes it

Cavitation is the most common of the avoidable failures. It occurs when pressure at some point in the circuit falls below the vapour pressure of the oil: vapour bubbles form and, as soon as pressure rises again, they collapse against the metal surfaces. Each implosion tears away a microscopic amount of material. Nothing of this is visible until the motor is opened.

On motors — unlike pumps, where the problem almost always starts on the suction side — the critical condition is the overrunning load: when the load drives the motor instead of the other way round. That is exactly what happens on a winch paying out, on a downhill conveyor or on a mill coasting to a stop: typical Hägglunds applications. At that moment the motor behaves as a pump and, if the circuit cannot feed the inlet fast enough, oil is missing precisely where it is needed.

The causes we most often find behind it:

• Insufficient boost pressure, or make-up (anti-cavitation) valves stuck or wrongly set
• Undersized return or feed line, throttled or partly obstructed
• Clogged filter increasing the pressure drop upstream
• Oil too viscous for the operating temperature — typical of cold starts, where the oil cannot keep up with demand
• Air drawn in through a fitting or a seal that is not tight on the low-pressure side

Cavitation and aeration are not the same thing, even though they reach the workshop with the same complaint. In cavitation the bubbles are vapour generated by the oil itself; in aeration it is free air drawn in from outside. The noise is similar — the metallic rattle maintenance crews describe as “gravel in the circuit” — but the cause to be removed is different, and getting the diagnosis wrong means seeing the same motor again a few months later.

What we find at teardown. Cavitation damage does not look like normal wear: it is not a uniform loss of material but a honeycomb erosion, spongy and localised, concentrated around the distributor timing area and the edges of the porting. It is recognisable at a glance to anyone who opens these motors regularly, and it is the reason dimensional inspection alone is not enough: a component can be within tolerance and still be compromised at the surface.

What we measure. On the test bench cavitation shows up as a drop in volumetric efficiency and increased internal leakage at the same pressure: the motor turns, but part of the flow does no work. These are the figures that go into the test report handed to the customer, and that allow the condition before and after the overhaul to be compared.

Can it be recovered? In most cases yes, if the erosion is confined to the sealing and distribution surfaces: the affected components are replaced with genuine parts and the fits restored. It becomes uneconomical when the erosion has reached the seats or the housing. But the real point is another: if the underlying cause is not removed, the damage comes back. That is why, together with the motor, we check the condition of the circuit — pressures, filtration and fluid condition, line sizing — and where necessary we work directly on the installation.

The overhaul process in the workshop

1. Initial diagnosis — symptoms, operating conditions and service history of the motor.
2. Complete disassembly and cleaning of all components.
3. Dimensional inspection of pistons, cam ring, distributor, bearings and shaft, compared against the manufacturer’s tolerances.
4. Detailed quotation listing the parts to be replaced, before any work goes ahead.
5. Replacement with genuine Hägglunds parts and new seals.
6. Reassembly to the manufacturer’s specifications and tightening torques.
7. Test bench testing with a documented measurement report, handed over to the customer.

Test bench testing

No motor leaves the workshop untested. TFS has a test bench for motors and cylinders, original Bosch Rexroth equipment, rated up to 420 bar, 74 l/min and 15 kW, able to take motors up to the size of a Hägglunds Viking MB84 — around 1,500 kg.

Testing measures flow, pressure, temperature, volumetric efficiency, internal leakage and noise. The customer receives the full test report: that is the difference between a motor that has simply been reassembled and one whose actual performance is known before it goes back into the line.

Lead times and genuine spare parts

Lead times depend on the size of the motor and on parts availability. The heaviest item is almost always sourcing the genuine spare parts, which takes around ten days on average. TFS works exclusively with genuine Hägglunds parts: on motors of this size, what you save on a non-genuine component does not offset the risk of a second breakdown.

For a concrete order of magnitude: the complete overhaul of a Viking MB84 documented in our case study — disassembly, inspection, genuine parts and testing — took 25 days in total.

Why choose TFS

• Hägglunds partner — see the page dedicated to the brand
• Hydraulics workshop specialising since 1997
• Test bench, original Bosch Rexroth, for documented testing
• Multi-brand overhauls: Bosch Rexroth, Kawasaki, Casappa, Parker
• On-site support, collection and delivery throughout Europe and the Mediterranean

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Frequently asked questions →

Which Hägglunds series does TFS repair?

All the main ones: CA and CAb, CB, CBm and CBp, Viking (MA and MB, including the MB84), Atom, Marathon and Compact, as well as complete Hägglunds Drive and Infinity systems.

Does the overhaul include testing?

Yes, always. Every motor is run on the test bench with measurement of flow, pressure, temperature, volumetric efficiency and internal leakage; the test report is handed over with the motor.

How long does a Hägglunds motor overhaul take?

It depends on the size and on the parts required. Sourcing genuine components takes around ten days on average; the complete overhaul of a Viking MB84 documented in our case study took 25 days in total.

How much does it cost to overhaul a Hägglunds motor?

The cost depends on the series, the size and above all on which components turn out to be out of tolerance at disassembly: two identical motors can need very different work. That is why dimensional inspection always precedes the quotation, which lists in detail the parts to be replaced before any work goes ahead.

Do you repair motors not purchased from TFS?

Yes. Overhaul is a service independent of supply: we work on motors installed by anyone and, if needed, we can also carry out bench testing alone on a component overhauled elsewhere.

Is TFS a Hägglunds partner?

Yes, TFS is a Hägglunds partner and works to the manufacturer’s specifications with genuine spare parts. The test bench used for testing is Bosch Rexroth certified.

Can a motor that has cavitated be recovered?

In most cases yes, when the erosion is confined to the sealing and distribution surfaces: the affected components are replaced with genuine parts and the fits restored. It becomes uneconomical if the erosion has reached the seats or the housing. In every case the underlying cause must be removed — boost pressure, lines, filtration, oil viscosity — otherwise the damage comes back.

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Case study: overhaul of a Viking MB84

A real job on a Viking series motor: overhaul of a 1,500 kg Hägglunds Viking MB84 fitted to the winch of an offshore vessel, which reached the workshop with noise and overheating. Complete disassembly, dimensional inspection against certified tolerances, genuine parts and bench testing before return: 25 days in total.

Further reading: authorised repair and testing

The same principle applies to every brand TFS handles: why being an authorised repairer matters — manufacturer procedures, genuine parts and bench verification before the component goes back.