Caterpillar 5I-8670 Hydraulic Filter (Pilot)

Fitment and Service Notes

The pilot filter is the smallest hydraulic element on the machine and the one that gets replaced least often, because nothing about it announces itself. It does not filter the oil that moves the boom — it filters the low-pressure oil that tells the machine how to move. That oil feeds the joystick controls, the travel pilot circuit, the solenoid valves and the pump regulators that convert operator input into swashplate angle. When the element is loaded, the machine still digs; it just responds late, and a good operator notices the machine feels tired long before the workshop does.

Two fitment cautions on this number. First, order by the number stamped on the element you are removing, not by the machine badge. Excavators that have been rebuilt or re-imported frequently carry mixed-generation components, which is common on used 320-family machines moving between Africa, the Gulf and Latin America. Second, this element appears on a very wide fitment list — from the 307D and 308D compact machines up through the 336D and the M325C MH wheeled excavator. A wide fitment list is useful for quoting and useless as a fitment guarantee: the thread and height have to match the housing in front of you.

For context on cost, quality aftermarket elements for these numbers typically run 30–60% below OEM list, which is why fleets servicing several 20-tonne machines buy the pilot and case drain elements together rather than one at a time. The rest of the set is on the site: the guide to the three hydraulic filter positions explains what the pilot, case drain and return elements each protect, the Cat 320D filter guide lists all seven service elements, the 179-9806 return filter page covers the 2,000-hour element, and choosing the right hydraulic filter explains how these elements are specified in the first place.

FAQ

Q: Which machines use the Caterpillar 5I-8670 filter?
A: 5I-8670 is the pilot (hydraulic) filter element listed for the Cat 320D, 320D L, 320D GC, 320D2 and 320D2 L, and fitment lists cover the wider 312C–336D excavator range as well as wheeled machines such as the M325C MH and W345C MH. The part number also appears on 307D, 308D and 312D listings. Cat changed hydraulic filtration across builds, so confirm against the number on the element you remove and your machine serial prefix.

Q: What does the pilot filter do, and what happens when it is blocked?
A: The pilot filter supplies clean low-pressure oil to the joysticks, travel pilot circuit, solenoid valves and pump regulators. When it loads up the machine does not stop working — it loses precision: slow or notchy controls, a machine that will not track straight, sluggish response once the oil is warm. Because no warning light is connected to it, pilot elements are commonly found years old at strip-down. Cat's schedule groups it with the 1,000-hour hydraulic service.

Q: What are the specifications and cross references for 5I-8670?
A: Per aftermarket listings it is a spin-on element with an M45 x 2.0 thread, roughly 155 mm overall height and about 87 mm largest outside diameter, with a gasket around 60.6 mm OD / 54.4 mm ID. Cross lists pair it with Baldwin BT9464, Donaldson P573481, Fleetguard HF35519, Sakura HC9901, HIFI SH66050 and SF Schupp SPH94010. Cat describes the position as an advanced-efficiency hydraulic (pilot) filter. Published dimensions vary by supplier, so treat them as a fitment check rather than a drawing.

Q: Is this pilot filter OEM or aftermarket, and how do I order it?
A: This is a high-quality aftermarket element cross-referenced to Caterpillar OEM 5I-8670, 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; we confirm the element and grade before dispatch. Stock items ship in 3–7 days, FOB Shanghai or CIF to your port.