Cummins ISB 5.9 Engine Rebuild Kits and Supporting Components

Engine Overview: Cummins ISB 5.9

The Cummins ISB 5.9 is a high-performance inline 6-cylinder diesel engine that delivers reliable power across a variety of industrial, construction, agricultural, and commercial applications. With a displacement of 5.9 liters and electronically controlled high-pressure fuel injection, the ISB 5.9 offers increased fuel efficiency, lower emissions, and superior durability compared to its mechanical predecessors (such as the 6BT).

This engine platform features a high-pressure common rail fuel system, robust cylinder head design, and a cast-iron block that supports extensive duty cycles. Common in medium-duty trucks, marine generators, farming equipment, and off-highway machinery, the ISB 5.9 remains a popular workhorse in the field—and a strong candidate for a full rebuild when maintenance or overhaul is required.

When to Rebuild: ISB 5.9 Rebuild Indicators

Rebuilding your Cummins ISB 5.9 is a critical step in maintaining engine longevity, power output, and fuel efficiency. Here are common signs that a rebuild kit may be necessary:

• Noticeable loss of compression or power under load

• Increased blow-by or crankcase pressure

• Elevated oil consumption or fuel dilution in the oil

• Excessive exhaust smoke (blue, black, or white)

• Poor starting performance

• High oil or coolant temperatures

• Low cylinder compression test readings

• Engine knocking, piston slap, or valve train noise

If any of these conditions are detected, an overhaul using a CPL-matched rebuild kit is often the most cost-effective and long-lasting solution.

ISB 5.9 Overhaul Kits by CPL Number

Each Cummins rebuild kit we offer for the ISB 5.9 engine is carefully matched by CPL (Control Parts List) to ensure precise compatibility with your engine configuration. Kits include pistons, rings, liners, rod and main bearings, cam bearings (if applicable), and a complete upper and lower gasket set.

Note: All kits below include standard size components unless otherwise specified. No pricing or part numbers are listed, as these are dynamic and may vary by region or supply chain status.

Cummins Rebuild Kit for ISB 5.9 (CPL 429, 2998, 8123, 8134, 8135, 8213, 8228, 8416)

This rebuild kit is designed for some of the most widely used ISB 5.9 variants, particularly those in heavy-duty commercial truck and industrial settings. These engines are known for their longevity but often begin to show wear between 10,000–15,000 hours depending on application.

Common failure symptoms for engines in this CPL group include:

• Increased crankcase pressure and oil seepage around the valve cover

• Cylinder scoring or piston wear due to long-hour operation

• Blow-by gas escaping from the oil dipstick or breather

Rebuild kit includes 1-piece pistons with standard compression ratio for CPL matching. If upgrading pistons or liners, confirm with a micrometer or bore gauge prior to installation.

Cummins Rebuild Kit for ISB 5.9 (CPL 2624, 8136, 8218, 8223, 8410)

These CPLs are associated with later-generation ISB 5.9 engines found in buses, power generators, and off-highway equipment. They often feature piston crown modifications or fuel mapping updates.

Rebuild recommendations:

• Inspect piston cooling nozzles during disassembly (see component below)

• Use proper valve lapping compound and feeler gauge during reassembly

• Verify head torque sequences match CPL-specific procedures

Supporting Components for ISB 5.9 Overhauls

To ensure a complete and reliable rebuild, the following components are commonly installed alongside a major overhaul kit.

Piston Cooling Nozzles

Nozzle to cool pistons for Cummins B, ISB, and QSB engines

• Required: one per piston

• Function: sprays oil onto the underside of the piston to control crown temperature

• Failure to replace may lead to piston overheating, ring sticking, or skirt scuffing

Recommended Replacement During Rebuild

Crankshaft Seal Kits (Front & Rear)

Front Seal Kit (w/ sleeve)

• Includes crankshaft front seal and wear sleeve

• Prevents oil leaks from the front timing cover

Rear Seal Kit (w/ double lip)

• Ideal for engines with wet clutch housings

• Prevents rear main seal leaks that may lead to clutch contamination

Install Tip: Always clean sealing surfaces and install with alignment tools when available.

Essential Engine Rebuild Tools

Having the right tools on hand is essential for a clean, damage-free rebuild. These are highly recommended for Cummins ISB 5.9 rebuilds:

Feeler Gauge (.002" to .025")

• Required for setting valve lash during rocker arm reinstallation

• Precision tool for intake and exhaust valve adjustment

• Range covers all required ISB 5.9 tolerance specifications

Piston Ring Assembly Tool

• Ensures proper ring orientation and avoids damage during piston installation

• Compatible with Cummins and Detroit Diesel applications

• Prevents cracked rings or scuffed liners during compression

Fuel Filter Removal Wrench (3-7/16" to 3-3/4")

• A must-have for removing spin-on filters without damage

• Avoids the use of channel locks or pipe wrenches that may crush the housing

Oil Filter Removal Wrench (4-21/32" to 5-5/32")

• Specially designed for large spin-on filters on ISB 5.9 engines

• Steel-strap design offers firm grip even on oil-slicked filter surfaces

Filtration Systems for Post-Rebuild Protection

Replacing fuel and oil filters during or after rebuild is critical to engine health and break-in performance.

Cummins Fuel Filter

• Diameter: 2.813"

• Height: 4.57"

• Thread: M16 x 1.5"

• Prevents injector scoring from water or contaminants

Fuel Filter & Water Separator

• Diameter: 3.02"

• Height: 5.62"

• Protects common rail fuel systems from moisture intrusion

Oil Filter (Spin-On Type)

• Diameter: 3.66"

• Height: 5.35"

• Thread: 1-16 UN

• Always pre-fill with clean oil before installation to avoid dry starts

Cooling System Service

Radiator Cleaner

• Effective against scale, rust, and sludge

• Non-corrosive to copper, aluminum, and cast iron components

• Should be used prior to coolant flush when overhauling cylinder heads

Temperature Control and Gauges

Temperature Switch

• Closes at 205°F

• Thread size: 1/2" NPT

• Works with analog and digital alarm systems

Gauges

• Mechanical Gauges (Standard and Alarm)

• Electrical Gauges (12V and 24V options)

• Recommended for monitoring oil pressure, water temperature, and voltage after rebuild

Expert Rebuild Tips for ISB 5.9 Engines

1. Match the Kit to the CPL – Always confirm your engine’s CPL number from the dataplate to ensure proper kit selection. Failure to do so can result in mismatched pistons, bearings, or head gasket sets.

2. Use Torque and Angle Specifications – ISB 5.9 engines often require angle torque (degrees) for head bolts. Do not rely on torque wrenches alone.

3. Inspect Cylinder Bores – Check for taper, scoring, or out-of-round conditions. Honing may not be sufficient if wear exceeds Cummins specs.

4. Clean Oil Galleries Thoroughly – Rebuilding without cleaning block passages can trap debris and ruin a fresh overhaul.

5. Use Break-In Oil – Always use a high-zinc break-in oil for the first 100 hours. Change after 25–50 hours for best results.

Why Diesel Pro Power?

With over 40,000 satisfied customers worldwide, Diesel Pro Power is a trusted source for Cummins ISB 5.9 rebuild kits, parts, and tools. We offer:

• Fast worldwide shipping

• CPL-specific product matching

• OEM-grade and aftermarket alternatives

• Multilingual customer support

• Secure checkout and warranty-backed products