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Cat C15 Engine

Cat C15 Engines For Sale

Yellow Caterpillar C15 Engine for Sale on top of a Wooden PlatformYou could say that the CAT C15 had a lot to live up to. After all, its job was to replace the coveted 3406E, arguably the best "Caterpillar yellow' engine ever assembled. Introduced in 1999, the CAT C15 shared much in common with the outgoing 3406E. And, given that the first run of C15's was virtually free of emissions control equipment (namely the code 6NZ power plants), early versions earned a reputation for durability and longevity, with many surpassing the million-mile mark. Naturally, these early C15's are some of the most highly sought after diesel engines from that era.

Structurally Sound

Though the C15 utilizes a straightforward inline-six design, its construction is extremely robust. Its cast-iron block integrates wet cylinder liners, and the liners is employs are triple O-ringed and equipped with a filler band for optimal sealing. Prior to ACERT technology arriving on the scene, the C15 even featured a heavy-duty stiffener plate between the block and oil pan. It boasts a single overhead cam (SOHC) arrangement, with a cast-iron, 24-valve cylinder head that benefits from six head bolts per cylinder. In the CAT C15’s early production (pre-ACERT), the engine made use of two-piece, aluminum skirt pistons (ACERT engines would enjoy one-piece steel pistons). For adequate cooling, all C15’s were graced with dual-nozzle piston cooling jets.

Bridge Engines

With tighter diesel emissions standards on the way, Caterpillar used what became known as “bridge engines” to bridge the gap between its early, emissions-free C15’s and the emissions-compliant C15 ACERT. The purpose of the bridge C15’s was to fill the void created by Cat’s inability to meet 2004 emissions standards at the EPA-enforced, October 2002 deadline due to its ACERT engines not yet being ready for production. The C15’s reputation suffered a blow during the bridge engine days, namely due to their tendency to run warm, consume excessive amounts of fuel, and also lack the same pulling power that 1999-2002 C15 engines had enjoyed. By 2004, the C15 ACERT arrived on the scene and the bridge engines were discontinued.

C15 ACERT (2004-2006)

CAT’s Advanced Combustion Emissions Reduction Technology (ACERT) debuted aboard the C15 in 2004 and, despite a few pattern problems, for the most part proved durable. Intake valve actuator (IVA) issues, either due to solenoid failure or problems with the solenoid’s wiring harness, is a common ailment faced by C15 ACERT owners. Unlike the pre-ACERT C15 engines, the C15 ACERT utilized a sequential turbocharger system (compounds). The compound arrangement relies on a smaller, wastegated turbo (known as the high-pressure unit) to get things started at low engine rpm, while a larger, low-pressure turbo takes over up top. CAT’s C15 ACERT also made use of a coolant-supplied pre-cooler, which was positioned ahead of the aftercooler within the intake tract.

C15 ACERT (2007-2010)

When CAT brought its SDP engines to market in 2007 (and many would argue that it was rushed to market), it was the beginning of the end for the C15 ACERT, as well as all of the company’s on-highway engines. In an effort to meet the 90-percent reduction in particulate matter (PM) over 2006 model year engines required by the EPA, 2007 versions were equipped with a diesel particulate filter (DPF), clean gas induction (CGI) and the CAT regeneration system (CRS). From the get-go, CAT’s new emissions reducing technology was troubled, costing owners and operators valuable uptime and high repair costs. In particular, the CRS system was plagued by injector issues, sensor defects, and fuel line problems.

C15 Similarities From 1999-2010

Throughout the C15’s production run, all engines used Caterpillar’s mechanically actuated electronically controlled unit injection fuel system (also known as MEUI). This injection system requires that roughly 100-psi of fuel pressure be delivered to the injectors by way of a rail in the cylinder head. From there, dedicated lobes on the camshaft (as well as an injector-specific rocker arm) actuate each fuel injector, mechanically, while the ECM tells the injectors’ electronic solenoids when to fire. All versions of the CAT C15 were also built with the aforementioned triple O-ring and filler band-equipped cylinder liners included. As for hard parts, every C15 used the same (or similar) oil pump, rod bearings, main bearings, and cam bearings.

Common Failure Points

Emissions system problems are rampant on 2004 to 2010 C15 engines, but the headaches are amplified even further on 2007 to 2010 models. The IVA-related issues mentioned above were the biggest source of downtime, but failure of exhaust aftertreatment sensors and components associated with the DPF are also highly common. And while mechanical failures are rare on the C15, cylinder liner protrusion is a big concern on higher mileage engines. Over time, the upper portion of the liner will often wear into the block’s deck surface. This causes the liner to tilt to one side, which typically leads to a blown head gasket. This is precisely why a liner protrusion test should always be performed during the overhaul of a C15, or during any head gasket repair. Below, you’ll find an extended list of the C15 failures we come across here at Big Bear Engine Company:

Logo of AERA Engine Builders Association

  • Spun Crankshaft Bearings
  • Cracked Cylinder Head(s)
  • Scored Pistons and Liners
  • Liner Protrusion
  • Over Fueling
  • Connecting Rod Failure
  • Oil Consuption and Extreme Blow By
  • Lack of oil pressure
  • Dropped Valves
  • Lifter/Roller Failure
  • Broken Exhaust Manifold Studs (early ACERT)
  • Cracked Exhaust Manifold (early ACERT)
  • Camshaft Failure
  • IVA Solenoid Failure

Caterpillar C15 Engine Replacement Options

Sadly, there are an array of issues that can immobilize your engine. Some instances result in your only option being full engine replacement. However, sometimes you may just need a few parts to bring it back to life, or maybe, the engine simply needs an overdue refresh. Of course, cost, time, and availability will all play a role in your final decision, which is why we offer complete, remanufactured long blogs.

Caterpillar C15 Engine Replacement Options

The Big Bear Remanufacturing Process

If a customer's C15 is unfortunate enough to suffer a serious internal engine failure but at the same time is fortunate in that many of the engine's external components can be salvaged, a remanufactured CAT C15 long block is a great solution. Coincidentally, a long block about as financially feasible as replacing an engine gets.

To accomplish this, our team of dedicated machinists and engine builders will perform a full core tear down, cleaning, inspection, and also handle all machining of the engine before it leaves our facility. This process ensures every Big Bear engine is in perfect running condition each and every time.

It's important to note, that all of our C15 Caterpillar remanufactured long blocks are built with a mixture of both reman and new parts. We do not recondition or refurbish old engine parts. Instead, we completely rebuild your Cat C15 back to OEM specs.

Thorough Cleaning

To avoid the early demise of both parts, and the C15 Caterpillar itself, we remove all impurities by stripping the block, head, rods and camshaft all of which are then thoroughly cleaned in a chemical jet wash or hot tank.


Each crankshaft is precision machined to exact tolerances, polished (for reduced bearing and oil resistance) and magnafluxed (to check for cracks). After that, the crankshaft is inspected by our quality control department.

Cylinder Head

To both ensure a proper sealing surface with the block and achieve a finish that is compatible with modern gasket materials, the cylinder head is resurfaced after passing initial inspection. Valve height is mic'd and the head is vacuum-tested to ensure correct valve sealing.


The C15's block is carefully inspected for cracks or other indications of damage. To eliminate cylinder distortion after the head is bolted and torqued to the block, the cylinders are bored and honed to precise tolerances. This process reduces the primary cause of engine blow-by. All block surfaces are machined and then inspected to achieve a proper finish.


Each C15 camshaft is inspected and precisely machined to guarantee correct lift. Lobes are also measured with a micrometer to make certain that all OEM tolerances are met.

Connecting Rods

The connecting rods are carefully inspected for sings of bend and/or twist. From there, rods are cleaned and then machined to OEM specifications. That process is followed with each unit being honed to its standard diameter of original equipment, which provides for even distribution of stress across the rod bearings. New bushings are fitted and machined in all bushed connecting rods.

New Parts

All new pistons and rings, bearings, cylinder lines, gaskets, and seals come standard on our remanufactured C15 Caterpillar long blocks. These new parts ensure dependable performance and reliability throughout the life of the engine. The new parts employed in a Big Bear long block are a combination of OEM and aftermarket components.

Further Insurance

Wearable parts are replaced in every single engine. All C15 Caterpillar core material is inspected and examined against the original specifications to certify correct dimensional tolerances. In the end, the goal of remanufacturing an engine is to restore it to a state that is as close to new as possible. Replacement parts are either new or requalified, and if new the parts are produced using the exact same manufacturing process(es) employed on the original engine. All testing is performed according to manufacturer specs and original production standards to ensure the highest level of quality.

Request a Quote

Please fill out the form below with your information and request. A member of our staff will be with you shortly.


CAT C15 Long Block Parts List:

  • Side View of Yellow Caterpillar C15 Engine for Sale Block
  • Cylinder Head (loaded and complete)
  • Crankshaft
  • Connecting Rods
  • Liners
  • Pistons and Rings
  • Camshaft
  • Lifters and Followers
  • Intermediate Cover
  • Timed Front Gear Group
  • New Upper and Lower Gasket Set
  • All Required Lower Gaskets and Seals
  • **1 Year Warranty

*Note: We can provide a new oil pump, oil cooler, water pump, turbo, injector and fuel pump for additional cost(s) with the long block, but these components will not come assembled to the engine.

**1-Year Warranty: First 6 Months Parts & Labor, Second 6 Months Parts Replacement Only. Ask your sales representative for a full copy of our remanufactured long block warranty.

C15 Applications and Uses

  • Agriculture
  • On-Highway
  • Aircraft Ground Support
  • Construction
  • Mining
  • Industrial
  • Earth Moving

CAT C15 Spec

Engine Data

ConfigurationInline-six (I-6), four-stroke diesel
Production1999-2002 (C-15), 2002-2003 (C-15 bridge engines), 2004-2010 (C15 ACERT)
BlockCast-iron with triple O-ring wet cylinder liners (with filler band) and dual-nozzle piston cooling jets
HeadCast-iron, 4 valves per cylinder, 6 bolts per cylinder
Emissions EquipmentACERT with variable intake valve actuation and diesel oxidation catalyst ('04-'06), ACERT with variable intake valve actuation (IVA), clean gas induction (CGI), diesel particulate filter (DPF) and Cat regeneration system (CRS) ('07-'10), U.S. EPA Tier 3 equivalent, EU Stage IIIA equivalent, Chine Nonroad III
Displacement927 ci (15.2 L)
AspirationSingle turbocharger (pre-ACERT) with air-to-sir aftercooler, sequential turbochargers (ACERT) with pre-cooler and air-to-air aftercooler (wastegated high-pressure turbo)
Compression Ratio18.0:1
RotationCounter-Clockwise (from flywheel end)
Weight3,090 lbs to 3,239 lbs
Combustion SystemDirect Injection
Width36.5-inches (926 mm)
Height48.3-inches (1,226 mm)
Length54.2-iches (1,377 mm)

Give us a call today at 844-340-4114 for immediate sales and support for the Cummins 4BT, Cummins 6BT, 6CT, ISC, 855, QSB 4.5 L or CAT 3306. If you have any questions, check out our FAQ Page. We are always ready to help or just listen to your crazy off-roading adventures!

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