Cummins ISX: 3 Most Common Problems

Preface: What You Need To Know First

It’s The Popular Kid

It goes without saying that the Cummins ISX is one of the most popular and well loved diesel engines on the road today. Initially released in 1998 as a response to tightening EPA emissions standards, the ISX replaced the N14, Cummins’ original workhorse engine.

The Cummins ISX is definitively North America’s most popular heavy-duty engine. And the only engine offered by every major Class 8 truck manufacturer. With horsepower ratings that range from 400-600 and up to 2050 pound-feet peak torque it’s no surprise that this engine is a favourite for fleet operators and drivers alike.


But despite the engine’s popularity, it isn’t perfect. Let’s run through some of the most common issues.


Simple specs. Superior performance.

Advertised Horsepower: (400hp, 298kW)(450hp, 336kW)

Peak Torque: (1450/1650 lb-ft, 1966/2237 Nm) (1550/1750lb-ft, 2102/2373 Nm)

Governed Speed: 1800 rpm

Clutch engagement torque: 1000 lb-ft, 1356Nm

Cylinders: 6

Dry Engine Weight: 2964lbs

3 Common Issues with The Cummins ISX

1. EGR Valve Leaks

Like many other engines with an EGR, the Cummins ISX is prone to typical EGR problems. On the ISX the culprit is often a leaky EGR valve. This can seem innocent enough but the problem will compound over time and it’s often difficult to diagnose.

What to look out for:

  • Fluctuating coolant consumption
  • Coolant consumption that’s faster than normal
  • White residue left behind by burnt coolant

If you suspect a leaking EGR valve, it’s best to bring your Cummins ISX to our experts.

2. Flattened Camshafts

Notoriously, every model and rendition of the ISX has had issues with the camshaft. It’s prone to flattening out. This is largely because of an issue with the rocker arms. An issue in production with the rocker arms starved the components of proper oil from which makes them stick and hit the camshaft. This will eventually cause the lobes to become flat.

There aren’t specific symptoms that will indicate whether you have these faulty rocker arms. So it’s very difficult to diagnose until you’ve already seen a drop in the performance of your engine.


3. Dropped Cylinder Liners

The ISX is a mid stock steel cylinder liner equipped engine. That means that from the factory you have a cylinder liner that goes into the engine block and it’s supported halfway down the liner. If a piston seizes the cylinder liner breaks at the bottom. If the connecting rod or piston gets free of the liner it starts to destroy the whole engine block. Which is not only obviously detrimental to your vehicle but also very expensive to fix. That’s why you’ll want to diagnose any issues early.

What to look out for:

  • Overheating engine block
  • A drop in pressure
  • Coolant leaks

Looking To Schedule Service? Get In Touch And We'll Respond Within 24 Hours.

Contact the team to schedule your appointment today

Fill out the form to get in touch with the team—give us details about your vehicle and we'll recommend the best course of action. Or, just leave your name and number and we'll reach out by phone.

Request A Quote
Calendar icon
Fit to your calendar

Adrenaline Diesel has extended service hours to ensure you get the best appointment time possible.

Speeding Clock icon
Fast turnaround

Sourcing parts for complex jobs is our specialty. We always aim for the fastest turnaround possible.