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The Bobcat S750 and Its Powertrain Configuration
The Bobcat S750 skid-steer loader was introduced in the early 2010s as part of Bobcat’s M-Series, designed for high performance in compact construction and landscaping applications. With a rated operating capacity of 3,200 lbs and a turbocharged Kubota V3800-CRTE4CB diesel engine producing approximately 85 horsepower, the S750 offered vertical lift path geometry, high-flow hydraulics, and Tier 4 Interim emissions compliance.
Bobcat, founded in North Dakota in the 1950s, has sold hundreds of thousands of skid steers globally. The S750 became a popular choice for contractors and rental fleets due to its balance of power, maneuverability, and attachment versatility.
Initial Diagnosis of a Locked Engine
A 2013 Bobcat S750 purchased at auction was found to have a seized engine. The drive belts for the hydraulic pumps, AC compressor, and alternator were removed, and the starter was tested off the machine—confirming it was functional. Attempts to rotate the engine manually via the flywheel failed, indicating internal mechanical seizure.
The engine in question, a Kubota V3800-CRTE4CB, is a 3.8-liter inline-four turbocharged diesel with common rail fuel injection. Known for its reliability, it nonetheless can suffer catastrophic failure if oil starvation or bearing damage occurs.
Terminology Clarification
After removing the engine and placing it on a stand, the oil pan, timing cover, and lower crankcase were disassembled. One main crank journal was found to be severely damaged—half missing and chewed up. Metal debris from the failed bearing had caused two additional main bearings to spin, and one rod bearing showed signs of heat seizure.
The crankshaft was deemed unusable, and the block’s bearing saddles were compromised. A machine shop confirmed that the block was likely beyond repair, though some cast iron blocks can be line-bored and sleeved depending on the extent of damage.
Sourcing a Replacement Block and Compatibility Challenges
The search for a replacement block led to confusion over part numbers. The Bobcat part number (7024361) did not easily cross-reference with Kubota’s catalog. Eventually, it was determined that the correct Kubota part number was likely 1J551-01012, though variations exist depending on fuel pump mount and front cover design.
Kubota V3800 blocks are available in multiple configurations, and while most share core dimensions, differences in accessory mounting can complicate installation. It’s safest to source a block from a Bobcat application, but with careful inspection, blocks from other V3800 variants can be adapted.
Rebuild Strategy and Component Evaluation
A new crankshaft was ordered, and the remaining engine components were inspected. One piston skirt showed scratching but was deemed borderline usable. The decision was made to replace it and re-ring the other three pistons. The camshaft had light scoring on the center journal, which was polished for reuse.
A new block was sourced from Bobcat, but its packaging raised concerns. It arrived wrapped in a tarp with no protective oil coating, and visible rust was found in the oil gallery. Scratches on the deck surface were deep enough to catch a fingernail and extended to the cylinder bore.
Recommendations for Engine Rebuilders
Rebuilding a locked Kubota V3800 engine in a Bobcat S750 is a complex but achievable task. From diagnosing a seized crank to sourcing compatible blocks and components, the process demands mechanical intuition, patience, and resourcefulness. While dealer support may be limited, the aftermarket and salvage market offer viable paths forward. With careful inspection and methodical reassembly, even a catastrophically failed engine can be brought back to life—restoring the S750 to its role as a compact powerhouse on the jobsite.
The Bobcat S750 skid-steer loader was introduced in the early 2010s as part of Bobcat’s M-Series, designed for high performance in compact construction and landscaping applications. With a rated operating capacity of 3,200 lbs and a turbocharged Kubota V3800-CRTE4CB diesel engine producing approximately 85 horsepower, the S750 offered vertical lift path geometry, high-flow hydraulics, and Tier 4 Interim emissions compliance.
Bobcat, founded in North Dakota in the 1950s, has sold hundreds of thousands of skid steers globally. The S750 became a popular choice for contractors and rental fleets due to its balance of power, maneuverability, and attachment versatility.
Initial Diagnosis of a Locked Engine
A 2013 Bobcat S750 purchased at auction was found to have a seized engine. The drive belts for the hydraulic pumps, AC compressor, and alternator were removed, and the starter was tested off the machine—confirming it was functional. Attempts to rotate the engine manually via the flywheel failed, indicating internal mechanical seizure.
The engine in question, a Kubota V3800-CRTE4CB, is a 3.8-liter inline-four turbocharged diesel with common rail fuel injection. Known for its reliability, it nonetheless can suffer catastrophic failure if oil starvation or bearing damage occurs.
Terminology Clarification
- Seized Engine: A condition where internal components are locked due to mechanical failure, often caused by bearing damage or overheating.
- Spun Bearing: A bearing that has rotated out of its seat, often damaging the journal and block.
- Crank Journal: The surface on the crankshaft where bearings sit and rotate.
- Main Gallery: The primary oil passage that distributes lubrication throughout the engine.
After removing the engine and placing it on a stand, the oil pan, timing cover, and lower crankcase were disassembled. One main crank journal was found to be severely damaged—half missing and chewed up. Metal debris from the failed bearing had caused two additional main bearings to spin, and one rod bearing showed signs of heat seizure.
The crankshaft was deemed unusable, and the block’s bearing saddles were compromised. A machine shop confirmed that the block was likely beyond repair, though some cast iron blocks can be line-bored and sleeved depending on the extent of damage.
Sourcing a Replacement Block and Compatibility Challenges
The search for a replacement block led to confusion over part numbers. The Bobcat part number (7024361) did not easily cross-reference with Kubota’s catalog. Eventually, it was determined that the correct Kubota part number was likely 1J551-01012, though variations exist depending on fuel pump mount and front cover design.
Kubota V3800 blocks are available in multiple configurations, and while most share core dimensions, differences in accessory mounting can complicate installation. It’s safest to source a block from a Bobcat application, but with careful inspection, blocks from other V3800 variants can be adapted.
Rebuild Strategy and Component Evaluation
A new crankshaft was ordered, and the remaining engine components were inspected. One piston skirt showed scratching but was deemed borderline usable. The decision was made to replace it and re-ring the other three pistons. The camshaft had light scoring on the center journal, which was polished for reuse.
A new block was sourced from Bobcat, but its packaging raised concerns. It arrived wrapped in a tarp with no protective oil coating, and visible rust was found in the oil gallery. Scratches on the deck surface were deep enough to catch a fingernail and extended to the cylinder bore.
Recommendations for Engine Rebuilders
- Always inspect new blocks for rust, machining inconsistencies, and shipping damage.
- Use plastigage to verify bearing clearances during reassembly.
- Replace all seals, gaskets, and wear components during rebuild.
- Flush oil galleries and passages thoroughly before assembly.
- Document part numbers and cross-references for future service.
- Auction machines should be treated as unknowns—assume worst-case scenarios and budget accordingly.
- Cut open the oil filter to inspect for metal debris before teardown.
- Maintain detailed records of part numbers and compatibility notes.
- Work with experienced machine shops familiar with diesel engine rebuilds.
- Avoid relying solely on dealer support; independent sourcing and research are often necessary.
Rebuilding a locked Kubota V3800 engine in a Bobcat S750 is a complex but achievable task. From diagnosing a seized crank to sourcing compatible blocks and components, the process demands mechanical intuition, patience, and resourcefulness. While dealer support may be limited, the aftermarket and salvage market offer viable paths forward. With careful inspection and methodical reassembly, even a catastrophically failed engine can be brought back to life—restoring the S750 to its role as a compact powerhouse on the jobsite.
