Caterpillar BU118
Maintenance schedule, common problems & OEM parts breakdown
The Cat BU118 is a hydraulically driven utility broom work tool, not a self-powered machine. It mounts to a carrier's quick-attach plate and runs off the carrier's auxiliary hydraulic circuit through a gerotor-type brush motor (about 393-395 cm3/rev), turning the bristle core at roughly 190-210 rpm on 30-86 L/min of flow at 145-241 bar, depending on the host machine's hydraulic output. It carries no engine, transmission, undercarriage, or onboard fluid systems of its own. Cat offers it in two bristle-core configurations, polypropylene-only and polypropylene/wire, with operating weight running about 470-488 kg (1,036-1,076 lb) depending on which core is fitted. It sits mid-size in Cat's utility broom line, between the narrower BU115 and the wider BU121, and is built to run on skid steer loaders, compact track loaders, multi-terrain loaders, and compact wheel loaders carrying a matching quick-attach and hydraulic flow range.
Configuration choice, not model-year change, is what separates BU118 units in the field. Polypropylene-only cores suit general yard and pavement sweeping, while polypropylene/wire cores add stiffness for packed dirt, gravel, or heavier debris that a pure poly core would just push around. No documented predecessor/successor chain ties into the BU118 name; it is one size point in a broom family (BU115/BU118/BU121) sold alongside Cat's separate angle-broom and pickup-broom lines. In the used and parts market, that makes fit and flow the questions that matter most: confirm which bristle core is fitted, match the carrier's auxiliary flow and pressure to the broom's rated range, and verify the quick-attach plate suits the intended host machine before buying. Because the tool carries no engine or undercarriage to depreciate, resale value tracks bristle-core condition, brush-motor case-drain health, and mount-plate wear more than hours on a meter.
Below: full specifications, fluids & capacities, the factory service schedule, common service parts, verified fault codes, what owners discuss, attachment guidance, the complete assembly directory, and a serial-number reference. Complete parts lists with full OEM part numbers, exploded diagrams, quantities, and fitment data are available free in Heavy Parts AI.
Caterpillar BU118 specifications
Engine
| Onboard engine | Not applicable. The BU118 is a hydraulically driven work tool with no onboard power unit; it draws hydraulic flow and pressure from the carrier machine's own hydraulic system. |
| Drive motor displacement | 393 cm3/rev (24 in3/rev) on the polypropylene-bristle configuration; 395 cm3/rev (24.1 in3/rev) on the polypropylene/wire-bristle configuration. |
| Drive method | Direct drive hydraulic motor turning the broom shaft; no belts or chains. |
Weights
| Operating weight, polypropylene configuration | 470 kg (1036.2 lb) |
| Operating weight, polypropylene/wire configuration | 485-488 kg (1069.2-1075.9 lb), varies by configuration |
Dimensions
| Overall width | 2115 mm (83.3 in), same across both bristle configurations |
| Sweeping width, polypropylene configuration | 1865 mm (73.4 in) |
| Sweeping width, polypropylene/wire configuration | 1800 mm (70.9 in) |
| Height | 793 mm (31.2 in), same across both configurations |
| Length, polypropylene configuration | 1490 mm (58.7 in) |
| Length, polypropylene/wire configuration | 1530 mm (60.2 in) |
| Brush diameter, polypropylene configuration | 660 mm (26 in) |
| Brush diameter, polypropylene/wire configuration | 665 mm (26.2 in) |
Performance
| Required hydraulic flow, polypropylene configuration | 30-83 L/min (8-22 gpm) |
| Required hydraulic flow, polypropylene/wire configuration | 30-86 L/min (8-23 gpm) |
| Optimal hydraulic pressure, polypropylene configuration | 145-227 bar (2100-3300 psi) |
| Optimal hydraulic pressure, polypropylene/wire configuration | 145-241 bar (2100-3500 psi) |
| Brush speed at maximum flow, polypropylene configuration | 190 rpm |
| Brush speed at maximum flow, polypropylene/wire configuration | 210 rpm |
| Carrier class | Sized for compact/skid steer and compact wheel loader class carriers with standard-flow hydraulics; exact model fitment varies by region and dealer, verify with local Cat dealer for a specific carrier. |
Service capacities (summary)
| Onboard fluid capacities | Not applicable. The attachment has no independent fuel tank, engine oil, or cooling system; it operates on the carrier machine's own hydraulic fluid supply. |
Values vary by configuration, region, and serial range — confirm against your machine before planning transport or lifts.
BU118 fluids & capacities
| System | Capacity | Recommended fluid |
|---|---|---|
| Engine crankcase (with filter) | Not applicable | BU118 is a hydraulically driven utility broom work tool with no onboard engine. It has no engine oil system of its own. |
| Cooling system | Not applicable | No engine and no cooling system on this attachment. Cooling is handled by the carrier machine, not the broom. |
| Fuel tank | Not applicable | No fuel tank. The work tool carries no combustion engine or onboard fuel supply. |
| Transmission / powertrain compartment | Not applicable | No transmission or powertrain compartment. Broom rotation comes from a hydraulic motor supplied by the carrier machine, not from an onboard drivetrain. |
| Final drives | Not applicable | BU118 has no final drives. It is a mounted attachment, not a self-propelled unit. |
| Hydraulic system and tank | Not applicable (no dedicated reservoir) | The broom has no hydraulic tank of its own. Its gerotor-type brush motor runs on hydraulic flow and pressure supplied by the host carrier (loader, backhoe, or skid steer). Required flow range is about 30-86 L/min (8-23 gpm) at an optimal pressure range of about 145-235 bar (2,100-3,400 psi); use whatever hydraulic oil grade the carrier machine's OMM specifies, matched to climate per that machine's viscosity chart. |
| Axles / differentials | Not applicable | No axles or differentials fitted. The broom rides on the carrier's wheels/tracks and has no drive axle of its own. |
| Grease points (bearings, pivots, bristle-core bearings) | Spec only — service quantity not listed by volume; apply until purged at each fitting per the lubrication schedule | Multipurpose chassis grease (Cat-type general-purpose/multipurpose grease, NLGI 2 EP-type) at outer and inner bristle-core bearings and any pivot/mounting points, per the periodic lubrication interval in the tool-mounted OMM holder. No separate low- or high-temperature grease variant is called out specifically for this work tool; use the general-purpose grease grade carried in the Cat lubricant line. |
Capacities are refill values from factory literature — always fill to the dipstick/sight gauge, not the number.
Caterpillar BU118 maintenance schedule
| Service interval | Tasks |
|---|---|
| Every 50 h |
|
| Every 250 h |
|
| Every 500 h |
|
| Every 1,000 h |
|
| Every 2,000 h |
|
| Every 4,000 h |
|
Servicing the BU118 beyond the schedule
Predictive Maintenance and Fluid Analysis
The BU118 carries no fluids of its own, so track wear through the carrier's hydraulic oil analysis instead. Watch case-drain flow off the gerotor brush motor: rising case-drain volume flags internal motor wear well before brush torque drops. Log brush speed (target roughly 190-210 rpm) against the carrier's flow setting each shift; falling speed at constant flow points to motor or coupling wear. Pair this with bristle-wear measurements against the core diameter to schedule bristle replacement before uneven wear starts stressing the drive coupling.
Corrective and Common Repairs
Common BU118 repairs center on the bristle core and the quick-attach interface, not an engine or drivetrain. Replace worn or broken polypropylene or polypropylene/wire bristle segments in sections rather than swapping the whole core when wear is uneven. Reseal or replace the brush motor shaft seal at the first sign of weeping near the case-drain port. Repair elongated pin bores or worn locking wedges on the mount plate before they cause play at the carrier's coupler. Replace abraded hoses and couplers on the auxiliary circuit rather than just tightening fittings.
Overhaul and Rebuild Points
Because the BU118 is a passive hydraulic tool, overhaul centers on the gerotor brush motor and core shaft, not an engine block. Rebuild or exchange the motor when case-drain flow rises or brush torque falls off, replacing the gerotor set, shaft seal, and bearings together. Overhaul the core shaft and drive coupling once spline wear shows, and replace the containment boot at the same time. Recondition the mount plate and pin bores if elongated past factory tolerance so the broom keeps a tight fit on the carrier's quick-attach.
Seasonal and Environment Servicing
Cold weather stiffens polypropylene bristles and can crack a frozen containment boot on start-up; let the carrier's hydraulics warm up before running the broom hard in freezing conditions. Store the BU118 with the core off the ground to prevent flat-spotting bristles, and cap the hydraulic couplers to keep moisture and grit out of the circuit during layup. In abrasive or wet environments, rinse packed mud and debris from the core end caps and mount plate more often, since trapped grit accelerates bearing and seal wear faster than the bristles themselves.
BU118 attachments & work tools
Machine type and size class
BU118 is itself a work tool, a utility broom attachment, not a base carrier machine. It sits in the mid/large-frame broom size class alongside the narrower BU115 and wider BU121, built for skid steer loaders, compact track loaders, multi-terrain loaders, and compact wheel loaders.
Sweeping width
Sweeping width runs about 1865 mm (73 in) with an overall width near 2115 mm (83 in) and brush diameter around 660-665 mm (26 in); operating weight is roughly 470-481 kg (1,036-1,060 lb) depending on bristle configuration.
Bristle/core material options
Standard core uses replaceable polypropylene and steel-wire bristle sections in combination. All-polypropylene and all-steel-wire replacement cores are offered for softer floor sweeping or heavier debris/spoil removal respectively, matched to surface and application.
Hydraulic drive arrangement
Direct-drive gerotor hydraulic motor with displacement around 393 cm3/rev (24 in3/rev) turns the brush core, reaching roughly 190-220 rpm at maximum flow depending on configuration. Required flow is about 30-86 L/min (8-23 gpm) at an optimal pressure band near 145-235 bar (2,100-3,400 psi), sized to standard-flow auxiliary circuits without needing electrical connection.
Carrier/coupler compatibility
Mounts via the universal quick-attach face plate common across the compatible skid steer, compact track loader, multi-terrain loader, and compact wheel loader lineup, so no dedicated bracket kit is needed on machines already fitted with the standard work-tool coupler. Confirmed fit list spans mid-size through large-frame carriers across recent skid steer/CTL/MTL/CWL generations; always cross-check hydraulic flow class against the specific carrier before ordering.
Dust control / sprinkler kit (option)
An optional water sprinkler kit with a broom-mounted water tank suppresses airborne dust during sweeping. It is a bolt-on option rather than a standard fitment and requires periodic tank refilling during operation.
Containment and wear components
Rubber boots on the front and sides of the broom housing contain debris and limit airborne scatter during sweeping. A bolt-on, replaceable cutting/wear edge along the lower housing protects the frame during operation.
Bristle down-force adjustment
Bristle down-force is adjustable to increase bite for tough applications, notably spoil and coarse-material removal after cold planing cuts. This lets the same core handle light floor-sweeping duty and heavier road-milling cleanup by changing preload rather than swapping tools.
All BU118 assemblies by section
Every catalogued assembly group for the Caterpillar BU118. Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.
Electrical System
249-7649 Connector As -Resistive Temperature Device
| 18***36 | Socket-Connector; (16-Ga To 18-Ga) | 24 |
| 24***49 | Connector As; -Resistive Temperature Device | 1 |
| 3E***67 | Ring-Retaining | 1 |
Frame And Body
211-9547 Frame Gp-Broom -61-In
| 21***47 | Frame Group-Broom; -61-In | 1 |
| 21***56 | Frame As | 1 |
| 21***38 | Skirt; (Front) | 1 |
211-9548 Frame Gp-Broom -75-In
| 21***48 | Frame Group-Broom; -75-In | 1 |
| 21***57 | Frame As | 1 |
| 21***39 | Skirt; (Front) | 1 |
217-6178 Frame Gp-Debris -61-In
| 16***19 | Bolt; (M24x3x180-mm) | 2 |
| 21***78 | Frame Group-Debris; -61-In | 1 |
| 21***80 | Frame As | 1 |
217-6179 Frame Gp-Debris -75-In
| 16***19 | Bolt; (M24x3x180-mm) | 2 |
| 21***79 | Frame Group-Debris; -75-In | 1 |
| 21***81 | Frame As | 1 |
Hydraulic System
256-0043 Lines Gp-Connecting
| 14***15 | Connector As | 4 |
| 15***17 | Cap-Dust | 1 |
| 15***18 | Cap-Dust | 1 |
219-1251 Motor & Lines Gp-Broom -Broom
| 06***25 | Nut-Slotted Jam | 1 |
| 21***51 | Motor & Lines Group-Broom; -Broom | 1 |
| 25***43 | Lines Group-Connecting | 1 |
Service Equipment And Supplies
219-1249 Film Gp -61-In
| 12***56 | Film; (Warning) (No Step) (On Top Of Hood Behind Cab On Each Side) (On Each Fender Flare) | 1 |
| 21***49 | Film Group; -61-In | 1 |
| 22***69 | Film-Warning; (Do Not Operate, Read Omm) | 1 |
219-1250 Film Gp -75-In
| 12***56 | Film; (Warning) (No Step) (On Top Of Hood Behind Cab On Each Side) (On Each Fender Flare) | 1 |
| 21***50 | Film Group; -75-In | 1 |
| 22***69 | Film-Warning; (Do Not Operate, Read Omm) | 1 |
267-5603 Plate & Film Gp
| 17***15 | Film; (Reflective)(Warning) | 4 |
| 26***03 | Plate & Film Group | 1 |
Work Tool Arrangement
221-1990 Broom Ar-Utility -75-In
| 15***15 | Plate-Identification | 1 |
| 16***89 | Tack-Fastener | 4 |
| 21***48 | Frame Group-Broom; -75-In | 1 |
221-1980 Broom Ar-Utility -61-In
| 15***15 | Plate-Identification | 1 |
| 16***89 | Tack-Fastener | 4 |
| 21***47 | Frame Group-Broom; -61-In | 1 |
Work Tools
219-1171 Brush Gp-Broom -75-In
| 16***71 | Kit-Brush; -Polypropylene | 1 |
| 16***72 | Kit-Brush; -Wire | 1 |
| 16***88 | Bristle As-Polypropylene | 40 |
219-1170 Brush Gp-Broom -61-In
| 16***69 | Kit-Brush; -Polypropylene | 1 |
| 16***70 | Kit-Brush; -Wire | 1 |
| 16***88 | Bristle As-Polypropylene | 34 |
242-7200 Brush Gp-Gutter
| 13***40 | Key-Square | 1 |
| 14***36 | Adapter; (Straight) (-6 Orb X -6 Orfs) | 2 |
| 14***72 | Elbow Group | 1 |
257-5229 Kit-Mounting -Gutter Brush
| 22***70 | Bracket As | 1 |
| 22***73 | Plate | 1 |
| 22***76 | Plate | 2 |
256-9335 Kit-Water Spray -Lines, Dust Control
| 00***86 | Connector-Hose (1/4-18nptf Thd) | 2 |
| 12***56 | Clamp-Hose | 10 |
| 17***92 | Coupling | 1 |
247-6742 Pump Gp-Diaphragm
| 16***63 | Motor-Electric; (12-Volt) | 1 |
| 24***42 | Pump Group-Diaphragm; -Water Spray | 1 |
| 24***23 | Head-Pump | 1 |
116-2001 Strainer Gp-Water
| 11***01 | Strainer Group-Water | 1 |
| 11***14 | Screen; (Water Tank) | 1 |
| 11***15 | Gasket | 1 |
BU118 serial number reference
The ID plate for the BU118 broom is mounted on the attachment itself, not on the carrier machine - if it is hard to read under dirt or paint, check the broom's main frame near the mounting/quick-coupler end first. Read it as a 3-letter prefix followed by a sequential number (e.g. HJS00001); the prefix marks the production/design series of the broom attachment, and the number is its position within that series. It does not encode the carrier machine's own serial number.
| Prefix | Identifies | Notes |
|---|---|---|
| HJS | BU118 Utility Broom, 1.9m (75in) broom class - early production series | Opens at HJS00001 (HJS1-Up). Filed under the BU118 model entry in Cat's parts-book system, covering the 75 in cutting-edge group, the broom-brush group, and the water-spray dust-control kit. Passive carrier-driven work tool, no engine of its own - a hydraulic motor off the carrier's auxiliary circuit drives the broom core. The same parts family also documents a BU115 (60/61 in class) run under a separate prefix (HJT) - do not carry that over to BU118. |
| LXB | BU118 Utility Broom, 1.9m (75in) broom class - later production series | Opens at LXB00001 (LXB1-Up). Documented as a later serial break for the same 75 in utility broom line, covering the broom motor-and-lines group. Parts-book titles for this break list BU115 alongside BU118, the same shared-family pattern seen on the HJS break, so that alone is not a sign this range is misfiled - but the exact HJS/LXB cutoff point is not spelled out anywhere found, so confirm the running change and cutoff serial with a dealer before ordering long runs against this range alone. |
Frequently asked questions
What engine does the Cat BU118 use?
None. The BU118 has no engine of its own. It is a passive hydraulic attachment that runs off the carrier machine's auxiliary hydraulic circuit through a gerotor-type brush motor (about 393-395 cm3/rev), which needs roughly 30-86 L/min of flow at 145-241 bar from the host skid steer loader, compact track loader, multi-terrain loader, or compact wheel loader.
What is the Cat BU118's operating weight?
About 470-488 kg (1,036-1,076 lb), depending on which bristle core is fitted. Polypropylene-only units run toward the lighter end of that range, and polypropylene/wire units toward the heavier end.
What replaced the Cat BU118?
No factory successor is documented for the BU118. It remains part of Cat's current utility broom lineup alongside the narrower BU115 and wider BU121. If a dealer confirms it has been discontinued in a given market, check current Cat attachment listings for the closest equivalent rather than assuming a direct replacement model.
What BU118 owners discuss
What hydraulic flow and pressure does the BU118 need from the carrier, and what happens if it's mismatched?
Poly vs wire bristle sections - which configuration and when to switch?
What's the single biggest driver of premature bristle wear that owners report?
Are there known motor or bearing failure patterns on this class of gerotor brush motor?
What quick-attach mounting wear shows up on brooms like this, and is it specific to Cat?
Does the BU118 have a hopper or a gutter brush option like some other Cat brooms?
What should a buyer check on a used BU118?
Compiled from owner and technician discussions across the industry — experiences vary by serial range and machine history.
Need a specific BU118 part?
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