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Cummins ISX Engine

Cummins ISX15 Engines For Sale

Red Cummins ISX 15 Engine for Sale

When production of the coveted and rock-solid reliable N14 Cummins drew to a close, Cummins launched its replacement: the ISX15. Originally referred to as the “Signature” series , the 912 cubic inch (14.9L) inline-6 was developed with more stringent future emission standards in mind. And in being built with future emissions standards in mind, the ISX15 effectively became one of the most reliable Class 8 diesel engines in modern history. Over the course of its 22-year production run, exhaust gas recirculation (EGR), a diesel particulate filter (DPF), and selective catalytic reduction (SCR) were all added to the ISX15. But unlike other engines manufactured in this era, the ISX15 retained its reputation for durability and even the promise of going 1 million miles before overhaul. The other part of the story is that the ISX15 became renowned for being one of the most fuel-efficient engines in its class and many would argue the ISX15 is one of the most fuel-friendly over-the-road diesels ever produced.

Engine Makeup & DOHC To SOHC

Front View of a Red Cummins ISX 15 Engine for SaleThe ISX15 displaces 912 ci thanks to its 5.39-inch bore and torque-friendly 6.65-inch stroke. The block is cast from gray iron and accommodates mid-stop, wet cylinder liners, and the cylinder head is made of cast iron as well. As for the valvetrain, the ISX15 made use of dual overhead camshafts (DOHC) form its inception until 2009. With the DOHC arrangement, one cam was dedicated to actuating the fuel injectors, as the early engines utilized unit injection. The second camshaft actuated the valvetrain and engine brake. Another notable way the ISX15 differed from the N14 it replaced was its use of full electronic control (the N14 did not). Beginning in 2010, when unit injection was scrapped in favor of high-pressure common-rail injection (called XPI, or Xtra-High Pressure Injection by Cummins), the design of the ISX changed from DOHC to single cam (SOHC).

Injection System & Turbo Changes

Cummins ISX Fuel Pump Holset TurboWhen Cummins reworked the ISX15 to accommodate its in-house, high-pressure common-rail injection system, the cam lobe problems that were inherent with cam-driven unit injection systems (on its DOHC engines) all but ceased. It also goes without saying that, fitted with common-rail injection, the ISX15 took a giant technological leap forward. The high-pressure fuel system produced injection pressures as high as 35,000 psi and utilized solenoid-actuated injectors that were capable of pulling off five injection events per combustion cycle. These precise injection events, coupled with extremely high pressure, were the key to meeting ultra-tight particulate matter (PM) emission standards. On top of that, the state-of-the-art injectors could pull off what are known as pilot (or “pre”) injection events, which reduce engine noise immensely. On the aspiration front, the Cummins ISX15 began its production run with either a Holset HX55W or HX60W (“W” for wastegate) turbocharger building boost, both of which were fixed geometry units. But beginning in 2003, the variable geometry Holset HE551V was introduced. The new VGT boasted improved responsiveness, which made adhering to emissions (namely PM) much easier. VGT technology took another leap forward in 2007 with the more advanced, Holset HE561VE, and then once more in 2010 with the introduction of the HE451VE.

Emissions Equipment

Exhaust Aftertreatment Diagram SCR Cummins ISXThe ISX15 was forced to change with the times. Luckily, Cummins built this into the engine's design, framing its ISX program around future emission standards and thereby making it significantly adaptable. In 2002, EGR made its way onto the ISX15 in order to meet the tighter, federal NOx emission standard that was fast approaching. In 2006, the ISX15 received a diesel particulate filter (DPF) in addition to EGR, the DPF being required to trap soot produced during combustion. The DPF was accompanied by regeneration cycles that periodically super-heated the DPF to transform the partuculate matter buildup into a fine ash for improved storage. By 2010, the EPA clamped down once again on NOx output and Cummins decided to meet the new standard by equipping the ISX15 with selective catalytic reduction (SCR). SCR technology calls for the use of diesel exhaust fluid (DEF) and, by working toward the same goal as EGR (curbing NOx), the technology ended up allotting the EGR system a much lighter workload. This lent itself to improved longevity of the EGR cooler, EGR valve, and the EGR system;s associated sensors.

The ISX15 Becomes The X15

X15 Cummins Class 8 Heavy Duty DieselAs the ISX15 design inevitably began to age, Cummins transitioned the platform into the X15, the ISX15’s replacement that was phased in starting in 2017. While mechanical, electronic, and emissions aftertreatment changes were present on the X15, it did retain the same bore and stroke, as well as a similar block, crankshaft, and connecting rods. To improve fuel efficiency on the Cummins ISX engines, a low friction water pump, geartrain, oil pump, and pistons were all added, which helps account for the X15’s fuel economy edge over its ’10-’20 model ISX15 predecessor. Three different types of engines were also made available at the X15 launch: the Efficiency Series, Productivity Series, and a higher compression Performance Series model, which the latter option boasting an available 605 hp and 2,050 lb-ft of torque.

Common ISX15 Problems And Failure Points

Cummins ISX 15 Engine for Sale Used on a CarAlthough it’s renowned for being one of the most reliable Class 8 engines in the modern diesel era, the ISX15 isn’t perfect. In fact, as the miles rack up it’s no different from any other heavy-duty diesel power plant, where age, wear and tear, operator abuse, and even maintenance neglect can land one in the shop—or worse. Starting on 2002 model year engines, EGR system issues abound with age, and include EGR cooler, EGR valve, and EGR pressure differential sensor failures. From 2006-onward, DPF problems rank high on the ISX15’s list of frequent problems, with DEF doser valves prone to failing on SCR-equipped engines ('09-on). But aside from emissions equipment failures, the ISX15 isn’t without its internal engine issues, and some of the most common hard-part failures we encounter here at Big Bear Engine Company are listed below:

  • Spun Crankshaft Bearings
  • Crankshaft Failure
  • Scored Pistons and/or Liners
  • Crooked Counterbores
  • Connecting Rod Failure
  • Camshaft Failure
  • Lifter/Roller Failure
  • Cracked Cylinder Heads
  • Dropped Valves
  • Overfueling
  • Lack of Oil or Oil Pressure
  • Excessive Blow By
  • High-Pressure Fuel Pump Failure

The ISX15 Remanufacturing Process At Big Bear Engine

When Whether a catastrophic engine failure occurs occurs or it’s simply merely time for an overhaul, our ISX15 ISX remanufactured long blocks fit the bill. Quick lead times, high-quality workmanship, low costaffordability, and a strong warranty highlight our long-block engine packages, —and we can match or beat the new engine option from a dealer in almost every every tangible way.

At the outset of all Big Bear ISX ISX15 remanufactured long block builds, our team of machinists and engine assemblers perform a full core tear down, cleaning, inspection, and also handle all machining of the engine before it leaves our facility. This These process processes guarantees that each ISX ISX15 we build leaves our care in perfect running condition every time.

It is important to note that all Big Bear ISX15 remanufactured long blocks are assembled using a combination of remanufactured and new parts. We do not recondition or refurbish old engine parts. Instead, we comprehensively rebuild your ISX15 ISX engine back to OEM specs.

Refer to the diagram here below to weigh the differences between replacing an engine through us, buying a new one from a dealer, going the in-frame route, or sourcing a used engine.

Replacement Options for Cummins ISX 15 Engine for Sale

Comprehensive Cleaning

Bare Black Cummins ISX 15 Engine for Sale

The remanufacturing process begins with every ISX15 engine undergoing complete disassembly. The block, head, crankshaft, connecting rods, and camshaft(s) are stripped and then thoroughly cleaned in a chemical jet wash or hot tank. This removes all contaminants and impurities that could potentially lead to early component wear and even premature engine failure.


Crankshaft of a Cummins ISX 15 Engine for SaleFactory ISX15 crankshafts are precision machined to exact tolerances, polished (for reduced bearing and oil resistance), and magnafluxed (to check for cracks). Then the crankshaft is thoroughly inspected by our quality control department.

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Cylinder Head

Cylinder Head of a Cummins ISX 15 Engine for Sale on top of a Wooden PlatformISX cylinder heads are resurfaced to ensure a proper sealing surface with the block, and we make sure they receive a surface finish that’s compatible with the latest head gasket materials on the market. Valve height is mic’d, and each head is also vacuum-tested to ensure precise valve seating.


Photo of a Long Block of a Cummins ISX 15 Engine for Sale on top of a Wooden Platform

For each ISX15 block, we use magnetic particles to meticulously check for cracks and imperfections in the casting. If the block passes inspection, the cylinders are bored and then honed to precise tolerances. On specific engines, torque plate honing is performed, which eliminates cylinder distortion after the head has been installed and torqued to spec. This process drastically reduces a major cause of engine blow-by. All block surfaces are machined and then inspected to achieve a proper finish.


Camshafts on a Cummins ISX 15 Engine for Sale Camshaft lobe wear and rocker problems are common on DOHC ISX15 engines. For both DOHC and later SOHC versions, we take care to fully inspect and then precisely machine every camshaft to ensure the correct lift is achieved. Camshaft lobes are measured with a micrometer to make certain that all OEM tolerances are met.

Connecting Rods

Connecting Rods of a Cummins ISX 15 Engine for Sale

Factory connecting rods are retained but undergo an extensive reconditioning process. This includes a thorough cleaning followed by careful analysis for indications of bend and/or twist. The ISX15 rods are then machined to OEM specifications prior to being honed to the standard diameter of original equipment for even distribution of stress across the bearings. New bushings are also installed and machined in all bushed connecting rods.

New ISX15 Parts

New Parts of a Cummins ISX 15 Engine for Sale

All Big Bear ISX15 long block packages receive a standard set of fresh components such as pistons and rings, bearings, wet liners, gaskets, and seals. Brand-new parts all but guarantee consistent, reliable performance throughout the life of your engine. The new parts included in our reman long blocks consist of a combination of OEM and aftermarket components, when available.

Further Insurance

Photo of a Complete Red Cummins ISX 15 Engine for Sale

To remanufacture an engine is to make it as close to new as possible. This is why wearable parts are replaced in every engine we build, and it's also why all ISX15 core material is closely inspected and compared with original manufacturer specifications to ensure correct dimensional tolerances. Replacement parts are either new or requalified and, if new, the parts are produced using the same manufacturing processes that were employed for the original engine. Finally, all in-house testing is performed to manufacturer specifications and original production standards.


ISX15 Long Block Parts List:

  • Block
  • Complete Loaded Cylinder Head
  • Crankshaft
  • Camshaft
  • Followers/Lifters
  • Pistons and Rings
  • Sleeves
  • Connecting Rods
  • Intermediate Cover
  • Timed Front Gear Group
  • New Upper and Lower Gasket Set
  • **1 Year Warranty

*Note: We can provide a new oil pump, oil cooler, water pump, turbo, injectors, and fuel pump for additional cost(s), 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 manufactured long-block warranty.

ISX15 Applications

  • Class 8 Heavy-Duty
  • Motor Coach
  • Well Servicing
  • Fire and Emergency
  • Industrial
  • Mining/Off-Highway


ISX15 Specs

Engine Data

Size14.9L (912 ci)
ConfigurationInline-six (I-6) Diesel
Bore and Stroke5.39-inch x 6.65-inch
BlockCast-iron with mid-stop cylinder liners
HeadCast-iron, 4 valves per cylinder
ValvetrainDual Overhead Cam (’99-‘09) (one cam actuated the fuel injectors, the second actuated the valvetrain and engine brake), Single Overhead Cam (’10-on) in conjunction with common-rail injection
Oil Capacity14 gallons
AspirationFixed Geometry Turbocharger (’99-‘02), Variable Geometry Turbocharger (’03-‘20)
Injection SystemCam-Driven Unit Injection (’99-‘09), Xtra-High Pressure Injection (XPI) Common-Rail (’10-‘20)
EmissionsEGR (’02-‘05), EGR, DPF (’06-‘09), and EGR, DPF, SCR (’10-end of production)
Production1998–2020 (its phase-out started in 2016 in favor of the X15)
Horsepower385 to 600 hp (depending on application)
TorqueUp to 2,050 lb-ft (depending on application)
Weight3,021 lbs (dry)

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 on our Cummins ISX engines, check out our FAQ Page. We are always ready to help or just listen to your crazy off-roading adventures!

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