विवरण
Fan motors in this class rarely die of old age. They die of the dirt that was already in the machine, and they take the replacement with them if the circuit is not cleaned out first. The 400702-00084 is the cooling fan drive motor used on the 49 to 53 tonne Doosan machines, and it is the part most often re-claimed within a season because the oil that destroyed the original was never changed.
Fitment
Supplied for the Doosan DX490 and DX530 excavators. Trade catalogues additionally list this number against DX380LC-3, DX450LC-7M, DX450LCA-7M, DX490LC-7M and DX530LC-7M machines, and the later Develon-badged versions of the same tonnage classes. Those lists come from supplier data rather than from a Develon parts book, so confirm against your own housing number and the machine serial prefix before ordering. If you are fitting a fan motor to a DX420 or DX500 instead, that is a different housing and we list it under our K1057295 fan motor.
What the unit looks like on the bench
A cylindrical upper housing steps down into a squarer lower port section, with a distinctive rectangular block on the side carrying one large central port and smaller peripheral connections. The output is a splined shaft retained by a hex nut and washer, running through a square four-bolt flange with counterbores. Cast marking A40M appears on the rear face of the units we ship. That combination, flange plus port block plus spline, is what your workshop should check against the removed part; two motors sharing a part number but coming from different build batches will not always share a port orientation.
Why these motors fail, in the order we see it
Contamination comes first. Particles scouring the interface between the sliding surfaces open up internal clearances, volumetric efficiency drops, and the fan stops reaching full speed at high idle. That is the slow failure. The fast one is the shaft seal: a case drain line that is kinked, blocked or routed through a restriction puts back-pressure on the seal lip, and the seal then leaks until the motor runs dry on its own lubrication film. Bosch Rexroth puts the case drain ceiling for axial piston units of this size at 2 bar absolute, which is a very small number and easy to exceed with a badly routed hose.
Heat is the third contributor. Hydraulic oil held above roughly 90 C loses viscosity, the film thins, and wear accelerates geometrically. That is why a machine with a plugged radiator core or a sticking main pump regulator chews through fan motors.
Oil cleanliness targets you can actually test
ISO 4406 reports cumulative particle counts per millilitre of oil in three size bands: 4 micron and larger, 6 micron and larger, and 14 micron and larger, each expressed as a range code. The lower the code number, the cleaner the oil. Reference points:
| Code example | Meaning | Where it applies |
|---|---|---|
| 20/18/15 | Minimum cleanliness Bosch Rexroth specifies for its A10VSO axial piston units | Baseline protection for pumps and motors in this class |
| 19/17/14 | Tighter target quoted for operation where drain fluid temperature reaches about 110 C | Hot quarry and demolition duty, high ambient |
| 18/16/13 | Commonly recommended for axial piston circuits in mobile equipment | Where the most sensitive component is an axial piston pump |
| 26/24/21 (indicative) | Oil that has been through a seal failure and shed material | Sample this and you will understand why the new motor did not survive |
Take a sample from the circuit before fitting a new motor. It costs nothing and it settles warranty arguments about whether the failure was the part or the oil.
Run this check before you order
Work down the list and stop at the first match. The full procedure with gauges and expected readings is in our 液压风扇马达诊断指南.
- Fan does not turn at all, circuit cold, motor warm to the touch. Check for seized bearing or hydrostatic lock from water ingress in the case drain. Suspect the motor.
- Fan turns slowly at every engine speed, no alarm. Measure flow at the fan motor ports. Low flow means the fan pump or its regulator, not the motor. See fan pump diagnosis.
- Fan speed correct but coolant still high. Look outside the hydraulic circuit: core plugging, thermostat, and the sensor itself, tested here.
- Oil temperature high, coolant normal, fan noisy at idle. Internal motor leakage bypassing to tank and heating the oil. Suspect the motor, and check the check valves in the fan circuit as covered in this guide.
- Previous replacement failed inside three months. Sample the oil for ISO 4406 and inspect the case drain routing before ordering again.
Supply terms
New aftermarket units carry a three to six month warranty as stated on your proforma invoice; genuine OEM parts and used cores are sold without warranty. Minimum order is one piece. We inspect each motor, photograph it for your confirmation, then pack it in a wooden case or to your specification. Small orders go by DHL, FedEx, TNT or EMS; volume orders ship by sea or air, with a delivery window of 5 to 8 working days from payment depending on stock. Monthly output on this line is around 300 pieces. Related Doosan parts are in the 斗山专区, and the wider range is under हाइड्रोलिक पंखा मोटर.
