Caterpillar 326-1644 Fuel/Water Separator

Fitment and Service Notes

This is the element that decides how long your main fuel filter lasts. Diesel arriving at site in drums, from roadside stations or from a bulk tank that has been sitting through a humid season carries free water and fine sediment; the separator is where the water is coalesced so it can settle in the bowl and be drained, and where the bulk of the dirt is caught. Skip it, or run it past its service life, and the water and dirt go straight into the 1R-0751 element behind it — which is why machines with "short filter life" usually turn out to have a separator problem.

Two details are worth checking before you buy. First, the supersession: 326-1644 replaced the earlier 1R-0770 element on these machines, and 326-1643 is the filter assembly — so a listing offering "326-1643 element" is describing the housing group, not a different element. Second, the number must come from your machine, not from the model year: Cat's 320D parts reference guide lists the 326-1644 for the standard 320D/320D L/320D GC, while MZD-prefix builds list a different fuel-side set (364-5287 and 438-5386). The stamped number on the old element plus the machine serial settles it in one message.

For the full 320D service set see the Cat 320D filter guide (oil 1R-0739, air 131-8821/131-8822, return 179-9806, pilot 5I-8670, case drain 093-7521), and for the symptoms and service discipline that keep a fuel system clean read excavator fuel filter problems: water, dirt & fixes. Buying for a container of machines still on the water? Collect element numbers and serials at the pre-shipment inspection and the filter set ships in the same container — see the used machinery inspection checklist.

FAQ

Q: Which machines use the Caterpillar 326-1644 fuel/water separator?
A: Cat's 320D parts reference guide lists the 326-1644 fuel/water separator element for the standard 320D, the 320D L and the 320D GC with the C6.4 engine. Aftermarket fitment lists cover a much wider group of C6.6/C7/C9-era machines: 320C, 320D, 320D L, 320D GC, 320D FM, 322C, 323D L, 325C L, 312C/312D, 315D L, 319D L, M325D, 953C/963C/973C track loaders and D5N/D5R/D6K/D6N dozers. Confirm against the number on your old element.

Q: Does 326-1644 replace 1R-0770?
A: Yes. The 326-1644 element supersedes the earlier 1R-0770 separator element listed for the same machines, and 326-1643 is the filter assembly the element fits. Supersessions like this are normal Caterpillar number changes across production rather than signs of a wrong part — but a seller quoting a separator number from a different engine class is a red flag worth checking.

Q: What does the 326-1644 separator cross-reference to?
A: Cross-reference lists pair 326-1644 with Baldwin BF1284-SP, Donaldson P550626 and P551110, and Sakura FS19820; some lists also carry 506853 alongside. Specifications on aftermarket sheets are approximately 108 mm outer diameter, 194 mm overall height and a 1"-14 UNF thread, with filtration accuracy listed at 99.9%. Cross numbers differ slightly between suppliers, so confirm the physical fit against the filter head before ordering in volume.

Q: Is this separator OEM or aftermarket, and how do I order it?
A: This is a high-quality aftermarket fuel/water separator element cross-referenced to Caterpillar OEM 326-1644, typically priced 30–60% below OEM list. Message us on WhatsApp or email sales@cn-machinery.com with your machine model, serial and the number on your old element — stock items dispatch in 3–7 days, FOB Shanghai or CIF to your port.