Caterpillarwork toolbroom-utility

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 engineNot 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 displacement393 cm3/rev (24 in3/rev) on the polypropylene-bristle configuration; 395 cm3/rev (24.1 in3/rev) on the polypropylene/wire-bristle configuration.
Drive methodDirect drive hydraulic motor turning the broom shaft; no belts or chains.

Weights

Operating weight, polypropylene configuration470 kg (1036.2 lb)
Operating weight, polypropylene/wire configuration485-488 kg (1069.2-1075.9 lb), varies by configuration

Dimensions

Overall width2115 mm (83.3 in), same across both bristle configurations
Sweeping width, polypropylene configuration1865 mm (73.4 in)
Sweeping width, polypropylene/wire configuration1800 mm (70.9 in)
Height793 mm (31.2 in), same across both configurations
Length, polypropylene configuration1490 mm (58.7 in)
Length, polypropylene/wire configuration1530 mm (60.2 in)
Brush diameter, polypropylene configuration660 mm (26 in)
Brush diameter, polypropylene/wire configuration665 mm (26.2 in)

Performance

Required hydraulic flow, polypropylene configuration30-83 L/min (8-22 gpm)
Required hydraulic flow, polypropylene/wire configuration30-86 L/min (8-23 gpm)
Optimal hydraulic pressure, polypropylene configuration145-227 bar (2100-3300 psi)
Optimal hydraulic pressure, polypropylene/wire configuration145-241 bar (2100-3500 psi)
Brush speed at maximum flow, polypropylene configuration190 rpm
Brush speed at maximum flow, polypropylene/wire configuration210 rpm
Carrier classSized 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 capacitiesNot 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

SystemCapacityRecommended fluid
Engine crankcase (with filter)Not applicableBU118 is a hydraulically driven utility broom work tool with no onboard engine. It has no engine oil system of its own.
Cooling systemNot applicableNo engine and no cooling system on this attachment. Cooling is handled by the carrier machine, not the broom.
Fuel tankNot applicableNo fuel tank. The work tool carries no combustion engine or onboard fuel supply.
Transmission / powertrain compartmentNot applicableNo transmission or powertrain compartment. Broom rotation comes from a hydraulic motor supplied by the carrier machine, not from an onboard drivetrain.
Final drivesNot applicableBU118 has no final drives. It is a mounted attachment, not a self-propelled unit.
Hydraulic system and tankNot 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 / differentialsNot applicableNo 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 scheduleMultipurpose 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 intervalTasks
Every 50 h
  • Inspect the bristle core (polypropylene or polypropylene/wire) daily for uneven wear, breakage, or missing bristles
  • Check the quick-attach mounting plate, pins, and locking wedges for looseness or wear before each shift
  • Inspect hydraulic hoses, quick-disconnect couplers, and fittings feeding the brush motor for leaks, abrasion, or loose connections
  • Verify brush rotation speed (roughly 190-210 rpm) matches the carrier's auxiliary flow setting
  • Clear packed debris from the broom frame, core end caps, and mount plate on a weekly basis
Every 250 h
  • Inspect the gerotor brush motor case-drain line and fittings for leaks or restriction
  • Check core shaft bearings and seals for play or grease weep
  • Inspect the containment/wiper boot around the motor shaft for cracking or dirt ingress
  • Measure bristle wear against the core diameter wear limit and rotate or index segments if wear is uneven
  • Torque-check mount plate fasteners and pin retention hardware
Every 500 h
  • Check case-drain flow from the brush motor to catch internal leakage before sweeping torque drops
  • Inspect the brush motor shaft seal and replace if weeping
  • Check core end bearings for radial play and repack or replace grease as needed
  • Inspect the broom frame and side skid shoes/wear strips for cracking or excess wear
  • Verify quick-attach wedge and pin bores are not elongated; re-shim or bush as needed
Every 1,000 h
  • Remove and inspect the gerotor brush motor internally for gerotor-set wear, scoring, or spline wear at the drive coupling
  • Inspect the core shaft and drive coupling for wear and replace worn splines
  • Inspect the full bristle core assembly and replace polypropylene or polypropylene/wire segments at or near the wear limit
  • Check frame welds and the mount plate for fatigue cracking after extended use
  • Flush and inspect the carrier's auxiliary hydraulic fittings feeding the broom for contamination
Every 2,000 h
  • Rebuild or replace the brush motor (gerotor set, shaft seal, bearings) as a unit
  • Replace core shaft bearings and the containment boot as a set
  • Inspect and, if needed, replace the entire bristle core assembly regardless of visible wear
  • Re-machine or replace the quick-attach mount plate pin bores if elongated beyond factory tolerance
  • Pressure-test hose assemblies feeding the broom motor before returning the tool to service
Every 4,000 h
  • Conduct a full teardown evaluation of the broom frame, core shaft, and motor mount to decide overhaul versus replacement
  • Replace all wear bushings, pins, and containment boots as a set
  • Recondition or replace the mount plate and coupler interface if worn past factory spec
  • Weigh continued rebuild cost against replacing the work tool outright, given typical attachment-class economics

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***36Socket-Connector; (16-Ga To 18-Ga)24
24***49Connector As; -Resistive Temperature Device1
3E***67Ring-Retaining1
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Frame And Body
211-9547 Frame Gp-Broom -61-In
21***47Frame Group-Broom; -61-In1
21***56Frame As1
21***38Skirt; (Front)1
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211-9548 Frame Gp-Broom -75-In
21***48Frame Group-Broom; -75-In1
21***57Frame As1
21***39Skirt; (Front)1
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217-6178 Frame Gp-Debris -61-In
16***19Bolt; (M24x3x180-mm)2
21***78Frame Group-Debris; -61-In1
21***80Frame As1
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217-6179 Frame Gp-Debris -75-In
16***19Bolt; (M24x3x180-mm)2
21***79Frame Group-Debris; -75-In1
21***81Frame As1
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Hydraulic System
256-0043 Lines Gp-Connecting
14***15Connector As4
15***17Cap-Dust1
15***18Cap-Dust1
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219-1251 Motor & Lines Gp-Broom -Broom
06***25Nut-Slotted Jam1
21***51Motor & Lines Group-Broom; -Broom1
25***43Lines Group-Connecting1
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Service Equipment And Supplies
219-1249 Film Gp -61-In
12***56Film; (Warning) (No Step) (On Top Of Hood Behind Cab On Each Side) (On Each Fender Flare)1
21***49Film Group; -61-In1
22***69Film-Warning; (Do Not Operate, Read Omm)1
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219-1250 Film Gp -75-In
12***56Film; (Warning) (No Step) (On Top Of Hood Behind Cab On Each Side) (On Each Fender Flare)1
21***50Film Group; -75-In1
22***69Film-Warning; (Do Not Operate, Read Omm)1
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267-5603 Plate & Film Gp
17***15Film; (Reflective)(Warning)4
26***03Plate & Film Group1
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Work Tool Arrangement
221-1990 Broom Ar-Utility -75-In
15***15Plate-Identification1
16***89Tack-Fastener4
21***48Frame Group-Broom; -75-In1
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221-1980 Broom Ar-Utility -61-In
15***15Plate-Identification1
16***89Tack-Fastener4
21***47Frame Group-Broom; -61-In1
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Work Tools
219-1171 Brush Gp-Broom -75-In
16***71Kit-Brush; -Polypropylene1
16***72Kit-Brush; -Wire1
16***88Bristle As-Polypropylene40
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219-1170 Brush Gp-Broom -61-In
16***69Kit-Brush; -Polypropylene1
16***70Kit-Brush; -Wire1
16***88Bristle As-Polypropylene34
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242-7200 Brush Gp-Gutter
13***40Key-Square1
14***36Adapter; (Straight) (-6 Orb X -6 Orfs)2
14***72Elbow Group1
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257-5229 Kit-Mounting -Gutter Brush
22***70Bracket As1
22***73Plate1
22***76Plate2
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256-9335 Kit-Water Spray -Lines, Dust Control
00***86Connector-Hose (1/4-18nptf Thd)2
12***56Clamp-Hose10
17***92Coupling1
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247-6742 Pump Gp-Diaphragm
16***63Motor-Electric; (12-Volt)1
24***42Pump Group-Diaphragm; -Water Spray1
24***23Head-Pump1
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116-2001 Strainer Gp-Water
11***01Strainer Group-Water1
11***14Screen; (Water Tank)1
11***15Gasket1
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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.

PrefixIdentifies
HJSBU118 Utility Broom, 1.9m (75in) broom class - early production series
LXBBU118 Utility Broom, 1.9m (75in) broom class - later production series

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?
Optimal range is 30-86 L/min (8-23 gpm) at 145-241 bar (2100-3500 psi), driven direct by a gerotor-type motor around 395 cm3/rev (24.1 in3/rev), giving roughly 210 rpm brush speed at max flow. Owners running these on the wrong circuit report two failure modes: below the minimum, the brush bogs and stalls in heavy material or wet debris; above the rated maximum, motor seals and bearings wear out early and warranty claims get denied. Confirm whether the carrier's auxiliary circuit is standard-flow or high-flow before hooking up, and match the spec plate rather than guessing off pump output alone.
Poly vs wire bristle sections - which configuration and when to switch?
Factory setup is a mixed poly/wire wafer pattern. Field consensus: all-poly sections for finish sweeping on pavement, light debris, and snow, since wire can scuff or gouge soft surfaces; all-wire or the mixed pattern for aggressive material like cold-planer spoil, packed mud, or gravel where poly alone won't clear the surface. Because the core is built from individual wafer sections on quick-release pins, mixing configurations section by section (poly up front, wire in high-wear zones) is common practice rather than running a single bristle type across the whole core.
What's the single biggest driver of premature bristle wear that owners report?
Excessive down-force. Community consensus across this class of broom attachment is consistent: the bristles should only flick the surface, not scrub or bend under load. Running the core too low burns through bristle length fast and can permanently bend or set the wafer cores out of shape. Replace bristle sections once remaining length gets down to about 110 mm (4 in) - past that point the flick action into the sweep pattern drops off noticeably and wear starts reaching the core faster.
Are there known motor or bearing failure patterns on this class of gerotor brush motor?
Main-shaft bearing and motor seal failures are the most expensive repair on this type of attachment, and owners trace most of them back to two causes: hydraulic contamination getting in through worn or leaking hose fittings, and sustained operation above the motor's rated flow. Wipe down and inspect the motor case, valve block, fittings, and hoses for weeping or staining at every bristle change rather than waiting for an obvious leak. A broom that feels weak or inconsistent is sometimes blamed on a bad motor when the real cause is a carrier-side relief valve or case-drain problem, so have your dealer verify actual motor case-drain flow before condemning and replacing the motor.
What quick-attach mounting wear shows up on brooms like this, and is it specific to Cat?
Not specific to this brand or model - it's a universal quick-attach wear pattern. Pins rotate in the mounting bore under load, and many frames aren't cross-drilled for grease, so the bores wallow out over time. The telltale symptom is a rattle or clunk in the mounting frame under load, or the broom skewing slightly during a pass instead of tracking straight. When checking a used unit, cycle the attach/detach lever, look for elongated pin holes, and feel for play between the broom frame and the carrier's quick-attach plate. This is a mounting-frame wear item, separate from anything hydraulic.
Does the BU118 have a hopper or a gutter brush option like some other Cat brooms?
No. The BU118 is a utility broom - it sweeps and casts debris to the side in forward or reverse travel, with no collection hopper and no gutter brush option. Those features belong to Cat's pickup broom line, which uses a different model designation. If a used listing shows a broom advertised as a BU118 but fitted with a hopper or a gutter brush, treat that as a red flag that the unit or the listing has been mislabeled, and confirm the actual model plate before buying.
What should a buyer check on a used BU118?
Start with remaining bristle length - it should be comfortably above the roughly 110 mm (4 in) replace point, and note whether the core is still the original poly/wire mix or has already been swapped to all-wire, which hints at heavier past duty in abrasive material. Check the gerotor motor for case leakage or weeping at the shaft seal, then cycle it and feel for chatter or uneven speed, a sign of worn internal lobes. Inspect the quick-attach mounting frame and pins for wallowed holes or looseness against the carrier's plate. Check hoses and couplers for cracking, abrasion, or non-factory field repairs. Also look at the rubber containment boots on the front and sides - torn boots are cheap to ignore but are a good indicator of overall care. Because true motor wear and hydraulic condition are easy to mask with a quick clean-up, have your dealer verify motor output flow and case-drain performance before agreeing on price.

Compiled from owner and technician discussions across the industry — experiences vary by serial range and machine history.

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