Diesel Diagnosis: Cummins ISX Camshaft Wear Causes And Problems With ISX Engines

Are you hearing a sudden engine knock or is your engine running rough? These can be signs that your camshaft is failing. Replacing a camshaft can be an expensive and frustrating repair. Especially if it needs to be done outside of an engine overhaul.


We know you want to do everything you can to keep your engine running for miles to come, and avoid unnecessary downtime. That's why today we're covering the problems you might see with the camshaft for the Cummins ISX.

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Common Cummins ISX Camshaft Problems

The ISX has gained a bit of a reputation for having issues with the camshaft. We're looking at where you be might seeing these problems and what you can do to keep your ISX running great.

Cummins Changes to Camshaft Rollers

If you're experiencing a camshaft failure in your ISX you probably want to know what went wrong. Cummins has changed the camshaft rollers multiple times to get more surface area between the roller and the cam. but differences in the camshaft lobes are designed to spread out pounds per square inch. That's basically the load on the camshaft.

Cummins ISX Camshaft Rollers

So you would think that the widest camshaft you could get would be the best. The problem however is the more surface contact you have, the more surface area there is to fail.

There's a lot to do with the start-up. You want to have a finish on the camshaft that's coarse enough that when the cam starts to turn for the first time, it gets the roller to turn with it and the roller doesn't slide. That's because you have a roller that has heavy down pressure on the camshaft. So if your roller doesn't start turning with the camshaft it will slide - which is the starting point for failure.

Avoiding Diesel Engine Camshaft Slide

The way to avoid camshaft slide is to do one of two things:

  • Narrow the camshaft

  • Make the surface coarse

How Wide or Smooth Should I Make It?

If you make it so wide and so smooth that it doesn't even roll, you've gone too far. That's the biggest battle with the camshaft and one of the big reasons that gasoline engines have started to move away from the camshaft. There's just too much opportunity for wear.

It's a good idea to take a look at your ISX camshaft when you have it apart for an overhaul. You might not think you need to take it in to get a valve adjustment done because it's running fine, but you might have valve clearances expanding or contracting. This can cause the cam rollers to beat on the cam.

So when you're doing an overhaul, take a look at your lobes and your rollers and make sure they're in good shape before you put it back together. They can and they will fail, and it's a lot of work to take it back apart.

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Problems With Cummins ISX Rocker Arms

Some ISX engines have had issues with rocker arms that have led to camshaft problems. Some productions of rocker arms prevented the correct amount of oil from flowing, which starved the components. These rocker arms begin to stick and smack the camshaft which leads to lobe flattening.

To fix this problem both the rockers and the cam need to be replaced. Otherwise, the faulty rocker arms will cause damage to your new camshaft as well.

Proper Oil Changes Help Prevent Camshaft Failure

It's important to do regular oil changes to ensure everything is working properly. It can be tempting to try and push it a few more thousand miles, but this can cause damage to your camshaft. And it could end up costing you more money and repairs than if you had just changed the oil regularly.

Doing oil samples can also help you diagnose an issue with your camshaft. It gives you a chance to check for metal shavings. These are often a symptom of failure and can damage other lobes on your cam. They can even travel downstream and damage other components.

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