Caterpillarwheel-type loaderwheel loader

Caterpillar 938H

Maintenance schedule, common problems & OEM parts breakdown

The Caterpillar 938H is a mid-size wheel loader in Cat's small wheel loader range, built for loading, load-and-carry, and general construction and aggregate work. The standard 938H uses a Z-bar loader linkage tuned for digging performance; Cat also built the IT38H integrated toolcarrier on the same chassis, with parallel-lift linkage suited to pallet forks and attachment-heavy material handling. Every 938H runs the Cat C6.6 ACERT inline six-cylinder diesel, rated at roughly 134 kW (180 hp) net power, paired with a four-speed-forward, three-speed-reverse powershift transmission. Operating weight runs about 15,050-15,100 kg (33,190 lb) depending on tire, bucket, and linkage configuration, with bucket capacities from roughly 2.3 to 3.0 cubic meters (3.0-3.9 cubic yards). Cat built the 938H from roughly 2007/2008 through 2013/2014, slotted between the 938G Series II it replaced and the 938K that succeeded it.

The 938H's biggest change from the 938G Series II was the engine: the G II's Cat 3126B ATAAC gave way to the C6.6 ACERT, adding roughly 20 hp net and meeting Tier 3-equivalent off-highway emissions rules. Cat also revised the axles with a standard front differential lock, offered an optional automatic front-and-rear lock, added load-sensing hydraulics, and increased lift and tilt breakout force over the G-series. Machines carry different serial prefixes tied to build plant and market rather than a mid-life redesign, so specs stay consistent across a given prefix run. In the parts and used-equipment market, the 938H sits in a strong spot within Cat's small wheel loader lineup: a multi-year, multi-plant production run kept supply plentiful, the C6.6 engine is shared across other Cat machines so parts and rebuild expertise are widely available, and enough working hours have accumulated on these machines that engine, transmission, and hydraulic wear patterns are well understood by rebuilders and parts suppliers.

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 938H specifications

Engine

Engine model	Cat C6.6 ACERT, inline 6-cylinder diesel, common-rail fuel system with waste-gate turbocharger
Gross power	147 kW (197 hp) at 2200 rpm, SAE J1995
Net power	134 kW (180 hp) per ISO 9249 / 80/1269/EEC; 133 kW (178 hp) per SAE J1349; flywheel power 128 kW (172 hp)
Displacement	6.6 L (402.8 cu in); bore 104 mm x stroke 127 mm (4.1 in x 5.0 in)
Peak torque	841 N·m (620 lb-ft) at 1400 rpm
Emissions tier	U.S. EPA Tier 3 / EU Stage IIIA

Weights

Operating weight	approx. 15,055 kg (33,190 lb); varies with bucket type and options
Static tipping load, full turn	10,076 kg (22,207 lb), with standard 2.8 m³ (3.65 yd³) general-purpose bucket and 20.5-R25 tires
Breakout force	122.6 kN / 12,508 kgf (27,576 lb)
Shipping weight	not published for this model as a distinct figure from operating weight; confirm transport weight by configuration with dealer

Dimensions

Overall length (bucket on ground)	7.19-7.35 m (23.6-24.1 ft), varies by bucket fitted and configuration
Width over tires	2.68 m (8.8 ft)
Height to top of ROPS/cab	3.35 m (11.0 ft)
Height to top of hood	2.41 m (7.9 ft)
Wheelbase	2.99-3.02 m (9.8-9.9 ft)
Ground clearance	0.38-0.40 m (1.25-1.3 ft)
Standard tire size	20.5R25

Performance

Max forward travel speed	43.1 km/h (26.8 mph)
Max reverse travel speed	25.4 km/h (15.8 mph)
Turning radius (outside, over tires)	12.04 m (39.5 ft)
Bucket capacity	1.8-3.4 m³ (2.3-4.5 yd³) heaped depending on bucket type; standard general-purpose bucket 2.8 m³ (3.65 yd³) heaped

Service capacities (summary)

Fuel tank	247 L (65.3 gal)
Hydraulic system	89 L (23.5 gal)
Engine oil (crankcase with filter)	17.4 L (4.6 gal)
Cooling system	36 L (9.5 gal)

Values vary by configuration, region, and serial range — confirm against your machine before planning transport or lifts.

938H fluids & capacities

System	Capacity	Recommended fluid
Engine crankcase (with filter)	17.4 L (4.6 US gal)	Cat DEO-ULS or Cat DEO multigrade diesel engine oil. Grade by ambient temperature: Cat DEO 10W-30 covers roughly -18°C to 40°C (0°F to 104°F); a full-synthetic 0W-40 or 5W-40 is preferred below -18°C; a straight 15W-40 is acceptable in consistently warm climates. Commercial heavy-duty diesel engine oil with a minimum 900 ppm zinc content is an acceptable alternate if Cat oil is unavailable.
Cooling system	36 L (9.5 US gal)	Cat ELC (Extended Life Coolant), premixed 50/50 or concentrate mixed with water. Gives roughly -37°C (-34°F) freeze protection at standard mix. Service life extends to 6 years/12,000 hours when treated with Cat ELC Extender at the midpoint interval; do not mix ELC with conventional coolant.
Fuel tank	247 L (65.3 US gal)	Ultra-low sulfur No. 2 diesel meeting the machine's fuel-quality spec. Biodiesel blends up to B20 are tolerated only when the blend stock meets Cat's biodiesel fuel spec; use a winter-blend or fuel additive in cold climates to prevent fuel waxing/gelling.
Power train (transmission)	43 L (11.4 US gal)	Cat TDTO (Transmission and Drive Train Oil). Grade by ambient temperature: TDTO 10W in cold climates, TDTO 30 as the general-purpose grade, TDTO 50 in sustained high ambient heat.
Front differential and final drives	57 L (15.1 US gal)	Cat TDTO, same grade selection as the power train, chosen by ambient temperature.
Rear differential and final drives	53 L (14.0 US gal)	Cat TDTO, same grade selection as the power train, chosen by ambient temperature.
Hydraulic system (tank)	89 L (23.5 US gal)	Cat HYDO Advanced 10 is the preferred hydraulic oil, rated roughly -20°C to 40°C (-4°F to 104°F) and giving an extended drain interval over alternates. Acceptable alternates if Cat hydraulic oil is unavailable: Cat DEO, Cat TDTO, or Cat MTO (Multi-Purpose Tractor Oil).
Grease (all lubrication points)	Per grease fitting, no reservoir total	Cat Multipurpose Grease (NLGI 2) is the standard grease, effective roughly -30°C to 40°C (-22°F to 104°F). Cat Extreme Application (XA) Grease is recommended for heavily loaded pins/bushings or wider temperature extremes.

Capacities are refill values from factory literature — always fill to the dipstick/sight gauge, not the number.

Caterpillar 938H maintenance schedule

Service interval	Tasks
Every 50 h	Check engine oil, coolant, and hydraulic tank oil levels before starting Walk around the machine and inspect tires, rims, and loader linkage pins for damage or leaks Test the back-up alarm, horn, lights, and seat belt condition Drain water and sediment from the fuel tank and check fuel level Grease the Z-bar loader linkage and lift/tilt cylinder pins Check transmission and differential/final drive oil levels
Every 250 h	Take an S·O·S engine oil sample ahead of the scheduled oil change Inspect and clean the radiator and hydraulic oil cooler cores Check alternator belt condition and tension Check battery terminals and electrolyte condition Clean or replace the cab fresh-air and recirculation filters
Every 500 h	Change engine oil and replace the engine oil filter Replace primary and secondary fuel filters Take transmission and hydraulic oil samples for S·O·S analysis Inspect service and parking brake function Grease articulation joint and steering cylinder pins
Every 1,000 h	Change transmission oil and replace the transmission oil filter Take differential and final drive oil samples front and rear Replace the hydraulic tank breather Replace the primary engine air filter element or sooner per the service indicator Inspect Z-bar linkage bushings and pins for wear
Every 2,000 h	Change front and rear differential and final drive oil Change hydraulic tank oil unless S·O·S results support an extended interval Test alternator and starter output Torque-check wheel rim bolts and loader linkage pin retainers Inspect engine and cab mounts for wear or cracking
Every 4,000 h	Check and adjust engine valve lash on the C6.6 ACERT Inspect the torsional vibration damper Extend the hydraulic oil change only if S·O·S analysis supports it Inspect turbocharger shaft play and wastegate operation
Every 6,000 h	Change engine coolant if running standard-life coolant on its base interval Pressure-test the cooling system and inspect hoses and clamps Inspect wiring harnesses and grounds for chafing or corrosion Replace the extended-life coolant extender if not doing a full coolant change

Servicing the 938H beyond the schedule

Predictive Maintenance & Fluid Analysis

Run S·O·S oil sampling on the C6.6 ACERT engine, powershift transmission, and front/rear differentials at every scheduled interval to catch bearing and gear wear before failure. Track transmission oil condition closely. The countershaft powershift is the 938H's most failure-prone system, and early solenoid or clutch wear shows up in fluid analysis before it becomes a shift-quality complaint. Sample hydraulic oil on the load-sensing system to justify extending the tank change interval. Log coolant condition to plan extended-life coolant renewal before scaling starts.

Corrective & Common Repairs

Hot-restart failures traced to the C6.6 ACERT's fuel system are the most reported field complaint on the 938H. Check for vapor lock and weak fuel transfer pump pressure before condemning the ECM. Intermittent loss of bucket hydraulics usually points to a worn or contaminated load-sensing pump rather than the tilt/lift valve. Hard or delayed shifting on the powershift transmission is typically a control solenoid or valve spool issue, not the clutch packs. Confirm with pressure taps before a teardown.

Overhaul & Rebuild Points

Z-bar loader linkage pins and bushings take the heaviest wear on digging-duty 938H units. Measure pin and bore clearance at rebuild rather than relying on visual inspection alone. IT38H toolcarrier machines wear differently, loading the parallel-lift linkage and coupler pins instead of the Z-bar set. Expect front differential and final drive rebuilds ahead of the rear on machines run with the automatic differential lock engaged heavily. When overhauling the C6.6 ACERT, check turbocharger and injector condition together, since ACERT fuel and air delivery are tuned as one system.

Seasonal & Environment Servicing

Cold-climate 938H operators should switch to an arctic-grade engine oil and confirm coolant freeze protection before winter, since the C6.6 ACERT's fuel system is prone to hot-restart problems that worsen after a cold soak. In hot, dusty aggregate or quarry environments, shorten air filter and radiator/hydraulic cooler cleaning intervals well below the standard schedule to prevent overheating. Wash accumulated material off the Z-bar linkage and differential lock components daily in abrasive conditions, and check tire pressure more often through temperature swings to avoid uneven wear on the 20.5R25 tires.

938H fault codes & troubleshooting

Code	Meaning	Likely cause	What to do
E284	Low brake accumulator pressure event	Discharged or leaking secondary-brake accumulator, low hydraulic oil level, faulty brake pressure sensor, or a stuck solenoid in the brake charging valve.	Check hydraulic oil level and condition first, confirm accumulator pre-charge, then test the brake pressure sensor and charging valve before condemning the charge pump.
E396-2	High fuel rail pressure event, engine derate	Faulty fuel rail pressure sensor, a sticking pressure-regulation valve, or a wiring fault sending a false high-pressure signal to the ECM.	Pull logged codes with a Cat diagnostic reader, inspect the rail pressure sensor wiring and connector, and verify actual rail pressure against the sensor reading before replacing parts. Code clears on key cycle if the underlying fault is intermittent.
E361-2 / E361-3	High engine coolant temperature event; -2 derates power, -3 forces shutdown	Low coolant level, plugged radiator core, slipping or failed fan drive, thermostat stuck closed, or a faulty coolant temperature sensor.	Shut down safely and let the engine cool, check coolant level and radiator fins for debris, and verify fan drive operation before restarting.
CID 0110 FMI 03/04	Engine coolant temperature sensor circuit, voltage above or below normal	Corroded connector, chafed harness, or a failed sensor causing an open or shorted circuit rather than a true over-temperature condition.	Inspect the sensor connector and harness for damage or corrosion, then check sensor resistance against spec before replacing it.
CID 0100 FMI 03/04	Engine oil pressure sensor circuit, voltage above or below normal	Damaged wiring, a loose or corroded connector, or a failed sensor rather than an actual low oil pressure event.	Verify real oil pressure with a mechanical gauge before trusting the sensor, then inspect wiring and connector condition.
CID 0190 FMI 08	Engine speed/timing sensor, abnormal frequency signal	Sensor air gap out of spec, sensor or tone-wheel damage, or a wiring/connector fault interrupting a clean speed signal.	Check sensor gap and mounting, inspect wiring for chafing or corrosion, clean or replace the sensor as needed.
CID 0248 FMI 09	Cat Data Link communication fault, abnormal update rate between control modules	Damaged data link wiring or connectors, a loose ECM connector, or a fault in the module that is supposed to be sending data (for example, transmission gear status not reaching the display).	Check data link harness continuity and connector condition between the engine, transmission/chassis, and display modules before replacing any single control module.
CID 1961 FMI 03/04	Hydraulic oil temperature sensor circuit fault	Wiring or connector damage, or a failed sensor, rather than an actual hydraulic oil over-temperature condition.	Inspect sensor wiring and connector, then verify actual hydraulic oil temperature with a handheld probe before replacing the sensor.

Codes and remedies are general guidance for this model family — always confirm with diagnostic tooling and your dealer before major repairs.

938H attachments & work tools

General-purpose buckets

Standard and heavy-duty general-purpose buckets for this class run roughly 2.3-3.0 m3 (3.0-4.0 yd3), with a 2.5 m3 (3.2 yd3) GP bucket offered specifically for the Fusion coupler. Sized for stockpiling, rehandling, bank loading and general excavating; the heavy-duty version is built for more aggressive digging.

Rock and coal buckets

Straight-edge rock buckets give higher breakout force and dump clearance for face or bank loading in quarry work; spade-edge rock buckets trade some capacity for better penetration in tougher material. Coal buckets are sized larger to match low-density material while keeping payload within machine limits.

Multi-purpose (4-in-1) bucket

Clamshell-action bucket adds bulldozing, grading, clamping (pipe or bulky debris) and topsoil stripping on top of normal loading. Mounts on the standard bucket linkage, no separate coupler required beyond the machine's usual attach point.

Material-handling and waste buckets

Flat-floor material-handling buckets move stockpiled aggregate and similar easy-load material at moderate breakout force. Waste/refuse buckets are a heavier-built version for transfer-station and sorting work in harsher duty.

Forks

Pallet forks and logging/millyard forks are offered pin-on or on the Fusion coupler for forestry and material-handling tasks. The 938H uses Z-bar loader linkage rather than the parallel-lift integrated-toolcarrier linkage of its IT-series sibling, so fork behavior follows standard Z-bar loader geometry, not toolcarrier self-leveling.

Coupler system (Cat Fusion)

Cat Fusion wheel loader coupler is available factory- or dealer-installed and gives near pin-on performance with fast tool changes, pulling the tool in close to the machine to help center of gravity and visibility. Straight pin-on mounting remains available for buckets and most work tools, and Fusion tools carry across other machines in the same coupler size class.

Auxiliary hydraulics for hydro-mechanical tools

A modular 3rd-valve kit, with a 4th function available as a further upgrade, adds an implement valve section and joystick control for tools needing independent hydraulic drive, such as rotary brooms or grapples. Kit is field-retrofittable onto a standard 2-valve lift/tilt machine.

Boom/linkage arrangement

938H is offered with standard-lift or high-lift (HL) boom arrangement; high lift adds reach and dump height at some cost to breakout force and cycle speed, and bucket lift specs shift between the two setups. Arrangement is picked to match the job, stockpile work versus truck loading height.

Brooms, rakes and grapples

Rotary/pickup brooms, land-clearing rakes and grapples are offered in this small-wheel-loader class, run through the 3rd/4th valve hydraulic kit and mounted via Fusion coupler or pin-on. Rakes suit land clearing and site cleanup; grapples handle brush, pipe, or bulky debris.

Guarding packages

Factory and dealer guard options protect the underside, cooling package and lighting for harsh-duty work such as quarry, waste or demolition-adjacent applications. Guarding is specified per application severity rather than sold as one fixed kit.

Ride control

Accumulator-based ride control is an available option to smooth travel with a loaded bucket or attachment at speed, cutting spillage and operator fatigue over rough haul routes.

All 938H assemblies by section

Every catalogued assembly group for the Caterpillar 938H. Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.

Hydraulic System

275-2263 Accumulator Gp-Ride Control -Charged

27***63

Accumulator Group-Ride Control; -Charged

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301-6924 Control Gp-Ride

13***00	Clip; (Tab)	1
14***64	Elbow, 90°,-8 Orb /-8 Orfs	1
14***88	Elbow Group	1
14***92	Elbow; (-12 Orfs/-12 Orfs Swivel)	1

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194-1723 Valve Gp-Check

16***49	Seal-O-Ring; (12.42mm Id)	1
19***23	Valve Group-Check; -Main Control Valve	1
2M***80	Seal--To Connector Pump Outlet	1
7X***76	Ring-Back-Up	1

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254-8094 Valve Gp-Ride Control

14***59	Plug	13
16***19	Plug As	1
19***23	Valve Group-Check; -Main Control Valve	1
1P***03	Seal - Rectangular (31.86mm Id)	1

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938H serial number reference

The PIN/serial plate on the 938H is mounted on the main frame at the operator's left (highway) side, near the front axle behind the front tire. The full stamped number is the Product Identification Number; the first three characters are the letter prefix tied to a specific build configuration, and the digits that follow are the sequential unit count within that prefix (for example, unit 726 built under the MJC prefix reads MJC00726).

Prefix	Identifies	Notes
MJC	938H wheel loader, standard configuration	Cat C6.6 ACERT engine. Most common prefix for this model; units documented from roughly 2007 through 2012 production. Factory service manual covers MJC1 and up.
JKM	938H wheel loader	Cat C6.6 ACERT engine. Factory service manual covers JKM1 and up, grouped with the LKM/MCC/MJC ranges in Cat's operation and maintenance literature for this model. Exact year span not separately documented - confirm with dealer.
LKM	938H wheel loader	Cat C6.6 ACERT engine. Factory service manual and parts catalog cover LKM1 and up. One equipment-spec listing ties LKM-prefixed units to Belgium assembly, spanning roughly 2007-2013.
MCC	938H wheel loader	Cat C6.6 ACERT engine. Factory service manual covers MCC1 and up. Auction/dealer listings show MCC-prefixed units built around 2009.

Frequently asked questions

What engine does the Caterpillar 938H use?

The 938H runs the Cat C6.6 ACERT inline six-cylinder diesel, rated at roughly 134 kW (180 hp) net power. It replaced the 938G Series II's Cat 3126B engine, adding about 20 hp net along with Tier 3-equivalent emissions compliance.

What is the operating weight of the Caterpillar 938H?

Operating weight runs about 15,050-15,100 kg (33,190 lb) for the standard configuration. Actual weight varies with tire choice, bucket size, and whether the machine is set up as the Z-bar 938H or the IT38H integrated toolcarrier.

What replaced the Caterpillar 938H?

The Cat 938K succeeded the 938H, with production overlapping around 2011-2013 as is typical of Cat's generational handoffs. The 938H itself had replaced the 938G Series II.

What 938H owners discuss

What's the most common engine complaint on the 938H, and does it tie to a specific engine series?

The 938H runs the Cat C6.6 ACERT, a 6.6 L (403 in³) inline six rated near 134 kW (180 hp) and certified to Tier 3 off-highway emissions. The most repeated complaint is a hot-restart failure: the loader runs fine all shift, gets shut down hot, then cranks but won't fire, or won't crank at all. Root cause traces to the high-pressure fuel system losing stable rail pressure under heat soak. Suspects include a weak high-pressure pump, a leaking check valve in the high-pressure rail, and the paired engine speed/timing sensors mounted low on the front cover under the pump. On higher-hour machines the injectors and high-pressure pump had never been serviced, which likely accelerated the failure. Cold no-start is a separate symptom and usually points to the pump not reaching normal running pressure rather than a hot-soak sensor fault.

Owners mention losing pilot pressure or getting slow, hesitant bucket dumping. What's behind it?

The 938H uses a load-sensing hydraulic system that sends flow and pressure to the implements only on demand. When owners report no pilot pressure or slow, hesitant bucket dumping, the fault usually sits in the pilot circuit, not the main pumps. A plugged pilot screen or a stuck or worn pressure-reducing valve restricts the signal that opens the main control valve. On at least one machine, swapping both hydraulic pumps did not cure a no-pilot-pressure complaint, which is why mechanics check the pilot screen and reducing valve before condemning a pump. Contaminated hydraulic fluid is the other repeat cause on this class of loader; it sticks control-valve spools and delays implement response. Have your dealer verify pilot pressure at the reducing valve before replacing a pump.

What wear patterns are typical for a 938H given it has no tracks?

As an articulated wheel loader the 938H has no track undercarriage. The equivalent wear points are the tires, the axle differentials, and the center articulation (hitch) pins. The upper and lower hitch pins ride on tapered roller bearings that spread vertical and horizontal loads; they hold up well on a regular grease schedule (Cat also offers a factory automatic lubrication option) but develop play and a clunk in the joint if greasing gets skipped. Tire wear and axle heat track closely to how much an operator spins the wheels loading into a pile. The differential lock and electronic traction control introduced on this model exist specifically to cut wheel spin and even out tire wear compared with earlier non-locking axles. A 938H showing feathered or mismatched tire wear, or a diff lock that won't engage, has usually been run hard without the lock in use.

What electrical or sensor gremlins come up on the 938H?

A recurring electrical complaint is total loss of non-switched power after shutdown: batteries test fine, the master disconnect tests fine, the starter still gets power, but the fuse block and everything else goes dead. That pattern points to a failed main power relay rather than a battery or ground fault. Separately, the Messenger display's diagnostic and service-mode screen can lock an owner out behind a password prompt that isn't documented outside dealer channels, which frustrates self-diagnosis of stored fault codes. Slow bucket dumping paired with a transmission warning light is another combination reported on this model; it usually traces back to a hydraulic pressure sensor rather than an actual transmission fault, so rule that out first.

Is a low brake accumulator pressure warning common on the 938H, and how serious is it?

Yes. A low brake accumulator pressure warning comes up repeatedly on the 938H's braking system and is usually resolved by recharging the accumulator with nitrogen to spec rather than replacing it. The accumulator stores pressurized hydraulic fluid so the service and secondary brakes still work with the engine off or if a pump fails, so this warning is a genuine safety alert, not a nuisance code to clear and ignore. A charge that keeps dropping on the same machine points to a leaking accumulator bladder or a faulty charging valve rather than a one-time low fill. Have your dealer verify accumulator charge and bleed the brake system to spec before returning the machine to work.

What should I check before buying a used 938H?

Confirm the engine and emissions tier match the paperwork. The 938H carries the Cat C6.6 ACERT engine at the Tier 3 level, without the diesel particulate filter and regeneration system of the later Tier 4 successor, which is part of why buyers favor it for simplicity. Ask for recent engine oil and hydraulic fluid sample results, and ask specifically when the injectors and high-pressure fuel pump were last serviced given how often neglected units show the hot-restart fault. Cycle every hydraulic function repeatedly, including a full lock-to-lock articulation swing and several bucket curl and dump cycles, to catch pilot-pressure hesitation or a sticking valve spool. Check that the brake accumulator holds charge with no low-pressure warning at start-up. Inspect the articulation hitch pins for play, which signals skipped grease intervals, and look for feathered or uneven tire wear that suggests the differential lock was rarely used. Have your dealer verify brake accumulator charge and pull stored fault codes before final purchase.

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

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