Description
Not every part number in a supplier catalogue appears in the manufacturer’s own web parts store, and we treat that as a fact to disclose rather than a detail to smooth over. 708-1S-00390 is one of those. Komatsu’s online catalogue returns nothing for it, while several independent trade listings describe the same number as the fan pump for a D375A-6, and the 708-1S prefix is consistent with a fan pump in Komatsu’s numbering.
What we can and cannot state
- Confirmed by pattern: the 708-1S prefix belongs to Komatsu’s hydraulic pump group, and the sibling numbers in that group are published by Komatsu as Pump Assembly.
- Trade-established, not manufacturer-confirmed: D375A-6 application.
- Not verified: displacement, pressure, flow, and any supersession relationship to other 708-1S numbers.
If you need certainty before ordering, the fastest route is a photograph of the plate on your old pump plus the machine serial prefix. We check those against the parts catalogue for your build and tell you if the number is wrong.
Why a D375-class fan pump fails
Large dozers work the hardest cooling duty in earthmoving: continuous high converter load, radiant heat from the engine and torque converter, and a core face that collects fine dust. The fan pump runs near maximum displacement for long periods, in oil that is hotter than the design point, and that combination is what wears the sliding surfaces. Once volumetric efficiency drops, the fan cannot reach speed, oil temperature climbs, and the machine derates.
Test before buying: clean the cores, measure pump output pressure and flow hot, and check the fan motor case drain. Our guide de diagnostic des pompes de ventilateur hydrauliques sets out the sequence, and the check valve article covers the case where every wear part is new and the oil still runs hot.
Montage
Match shaft spline, pilot, flange, port positions and control orientation against the removed pump. Prime the casing with clean oil before cranking. Change the return filter element and clear the suction strainer, targeting ISO 4406 18/16/13. Keep the case drain unrestricted to tank. Prove full fan speed under load and log temperatures.
Commande
Commande minimum une pièce. Garantie de trois à six mois sur les unités neuves du marché de l'après-vente, telle qu'indiquée sur votre facture proforma. Contrôlée au banc et photographiée conformément à votre commande avant fermeture de la caisse en bois, livraison sous 5 à 8 jours ouvrables à compter du paiement, sous réserve de stock. La gamme se trouve sous Moteur de ventilateur hydraulique Komatsu.
