What is blow-by, and why does it matter? If you’ve got a 5.9 Cummins under the hood, you may have heard of this dreaded phenomenon, where combustion gases leak past the piston rings and into the crankcase, creating all sorts of trouble. It’s a problem that can escalate quickly, leading to decreased engine performance, increased oil consumption, and eventually catastrophic engine failure. But don’t despair just yet – with timely intervention and a few proven techniques, you can tame blow-by and keep your Cummins running strong:

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Step 1: Pinpoint the Cause

The key to effectively tackling blow-by is to determine its root cause. Common culprits include worn or broken piston rings, glazed cylinder walls, and a compromised turbocharger. Here’s a closer look:

• Worn Piston Rings: Rings are critical for sealing the combustion chamber, but they can succumb to wear or breakage over time, creating pathways for blow-by.
• Glazed Cylinder Walls: When cylinder walls become excessively smooth, they lose their ability to maintain a proper oil film, leading to poor ring-to-wall contact and excessive blow-by.
• Turbocharger Issues: A faulty turbocharger can cause excessive boost pressure, putting strain on piston rings and potentially causing blow-by.

Step 2: Engine Overhaul

For severe blow-by cases, a complete engine overhaul may be necessary. This involves removing the engine from the vehicle, disassembling it, and replacing worn components. Here’s what entails:

• Boring and Honing: To restore the proper surface finish and tolerance to cylinder walls, they need to be bored (enlarged) and honed (smoothed) to specific dimensions.
• Installing New Pistons and Rings: Replace the old rings and pistons with new, factory-spec components. Ensure that ring gaps are set to manufacturer’s specifications.
• Checking Piston Clearances: Double-check the clearance between pistons and cylinder walls, as proper clearance is vital for optimal ring function.
• Replacing Other Components: As part of the overhaul, consider replacing other wear-prone components such as bearings, gaskets, and seals.

Step 3: Piston Soak and Decarbonization

In certain cases, a less invasive approach may suffice, such as piston soak and decarbonization. This involves:

• Piston Soak: Pour a specialized solvent into the cylinders and let it sit overnight. The solvent helps dissolve accumulated carbon and varnish, freeing up stuck rings.
• Decarbonization: Use a chemical cleaner designed specifically for removing carbon deposits. Spray it into the cylinders and follow the manufacturer’s instructions.

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Step 4: Catch Can Installation

To minimize the amount of blow-by gases entering the intake system, consider installing a catch can. This device traps oil and particles, reducing emissions and protecting the engine from further deterioration.

How To Fix Blow By On 5.9 Cummins

Conclusion

Fixing blow-by on a 5.9 Cummins can be a challenging task, but with the right approach, it’s certainly doable. By understanding the underlying causes and employing appropriate repair techniques, you can revive your Cummins’ performance, extend its lifespan, and get back on the road with confidence. Remember to address the problem in a timely manner to prevent irreversible damage and preserve the longevity of your beloved engine.