The CCV System on the 6.7 Cummins
How the Factory CCV Routes Blow-By Into the Intake
Every internal combustion engine produces blow-by, which consists of combustion gases and oil vapor that slip past the piston rings and pressurize the crankcase. Left unchecked, that pressure would build until seals fail, oil leaks everywhere, and you've got a much bigger problem than a rough idle.
The factory solution on the 6.7 Cummins is a Crankcase Ventilation (CCV) system that routes those blow-by gases from the valve cover back into the intake horn, ahead of the turbocharger. The idea is straightforward: instead of venting oil vapor into the atmosphere, the engine re-ingests it and burns it off during combustion.
The CCV filter is supposed to separate most of the oil mist from the vapor before it hits the intake. In theory, the air re-entering the intake should be mostly clean. In practice, especially on high-mileage or hard-working engines, that filter doesn't catch everything.
Why This Is a Problem on High-Load Cummins Applications
Here's where it gets real. On a truck that spends most of its time cruising at highway speeds with a light load, the factory CCV setup is manageable. The blow-by volume is relatively low, the oil mist is minimal, and the coalescer element keeps up.
Put that same engine to work and blow-by volume increases significantly. Hotter crankcase temps, higher cylinder pressures, and more combustion gas slip-by all mean more oil-laden vapor getting pumped right back into your intake stream. That oily mist coats the intercooler, fouls the intake manifold, and in the worst cases, starts affecting how the turbo's compressor wheel operates.
This is not a theoretical problem. It's one of the most common complaints from 6.7 Cummins owners who use their trucks the way they were built to be used.
Symptoms of CCV Issues on the 6.7 Cummins
Before you start pulling parts, it's worth confirming that your CCV is actually the culprit. These are the tell-tale signs:
Oily Intercooler Pipes and Intake Manifold
Pop the intercooler boots and take a look inside. If you find a slick film of brown or dark oil coating the inner walls of the charge pipes, that's re-ingested crankcase vapor. A little moisture inside is normal; visible oil coating is not. The same goes for the intake manifold. Pull the air horn and inspect with a flashlight. Oil streaking or pooling inside means your CCV is already putting contamination into the intake.
Excess Crankcase Pressure
An easy field check: with the engine at idle, remove the oil fill cap. If you feel positive pressure pushing out, or if you see oil vapor visibly escaping, your crankcase is building more pressure than the factory CCV system can handle. Some Cummins owners notice the oil fill cap actually getting pushed off, which is a serious sign of CCV system overload.
Turbo Contamination
This one's the most expensive consequence. Oil vapor entering the intake passes directly through the turbo's compressor side before it reaches the combustion chamber. Over time, that oil bakes onto the compressor wheel and housing, contributes to shaft seal wear, and can throw off compressor efficiency. If you've had unexplained boost issues or noticed oil residue at the compressor inlet, the CCV system is the first place to look.
CCV Reroute Kit: What It Does
A CCV reroute kit solves the problem at the source by redirecting crankcase blow-by away from the intake entirely, or running it through a catch can that traps the oil before it can contaminate your induction system.
Separates Oil Mist from the Intake Stream
The core function of any quality CCV reroute kit is oil separation. Instead of allowing the crankcase vapor to dump directly into the intake tract, the reroute kit either vents it to atmosphere through a breather filter or runs it through an inline catch can that collects the oil. What hits the atmosphere is cleaner air with the liquid oil fraction already removed.
The result: no more oily film coating your intercooler pipes, no more contamination building up in the intake manifold, and a much cleaner operating environment for the turbocharger.
Vent-to-Atmosphere vs. Catch-Can Options
There are two main approaches to the CCV reroute on a 6.7 Cummins:
- Vent-to-Atmosphere (VTA): The crankcase vent line is redirected out from under the truck, typically with a small breather filter at the end of the line. Oil vapor exits to the atmosphere rather than the intake. This is the simplest setup and keeps oil contamination completely out of the intake system. The trade-off is a small amount of oil mist released to the air, which is worth noting depending on your operating environment.
- Catch-Can: A canister is plumbed into the CCV line. Blow-by gases pass through the can, the oil droplets collect in the bottom, and cleaner vapor continues out of the vent port. The can needs to be emptied periodically, anywhere from every oil change to every few months depending on your duty cycle. This is the preferred setup for trucks that need to pass visual inspections, and it keeps any oily residue contained.
For hard-working 6.7 Cummins trucks, either option is a massive improvement over the factory setup. Browse the full selection of CCV reroute kits to compare options for your specific year and configuration.
Installation on the 6.7 Cummins
CCV Port Location on the 6.7 Cummins
On the 6.7 Cummins, the CCV system originates at the valve cover on the driver's side of the engine. The breather hose exits the valve cover and routes forward, connecting to the intake air horn ahead of the turbocharger. This is where you'll be making your modifications — either capping the factory intake connection and redirecting the line, or inserting a catch can into the existing circuit.
The CCV filter element itself is housed inside the valve cover assembly. On high-mileage trucks (generally 100K+ miles), it's worth inspecting or replacing the filter element before installing the reroute kit, since a saturated or degraded filter element will flow more oil than a healthy one.
Step-by-Step CCV Reroute Process
Here's a general walkthrough for a typical 6.7 Cummins CCV reroute installation. Always follow the specific instructions included with your kit:
- Gather your tools. Most installations require basic hand tools — combination wrenches, socket set, pliers, and hose clamp pliers. Have rags on hand for any residual oil in the factory lines.
- Locate and remove the factory CCV hose. Trace the breather hose from the valve cover fitting to where it connects at the intake horn. Loosen the clamps at both ends and remove the hose. Set it aside — you won't be reusing it.
- Cap the intake horn port. The factory intake connection needs to be sealed so no unfiltered air enters the intake. Most kits include a block-off plug or cap sized for this port. Install it with thread sealant or per kit instructions, torque it down snugly.
- Install the catch can or breather filter.
- If using a catch can, mount the canister to a solid bracket location in the engine bay where it won't contact hot surfaces or moving components. Route the inlet hose from the valve cover fitting to the catch can inlet port, and secure with the supplied clamps. Route the outlet to atmosphere with the provided breather filter, or re-route it to the clean side of your air intake system depending on your kit design.
- If running VTA, simply route the line from the valve cover fitting down and away from heat sources, terminating with the breather filter.
- Check all connections. With the engine cold, start it up and let it warm to operating temp. Inspect every connection for any signs of oil seeping at the fittings or hose clamps. A proper installation will be dry at all joints.
- Clear any residual codes. If your truck had a check engine light related to crankcase pressure or boost system performance, clear the codes after verifying the install is solid.
Maintenance: Emptying the Catch Can
If you went the catch-can route, maintenance is simple but necessary. Check the catch-can level every oil change interval. On a healthy 6.7 Cummins under normal use, you might see a few ounces of oil collected per interval. On a high-mileage engine with worn rings, or one that sees heavy towing regularly, collection rates can be higher.
Drain the catch can by removing the drain plug or separator bowl. Dispose of the collected oil properly. Do not let the catch can fill to capacity; an overfull can will push oil-saturated vapor back into the system.
Pairing the CCV Reroute with a Delete Kit
Why EGR Delete + CCV Reroute Together Makes Sense
If you're already running a delete setup on your 6.7 Cummins, pairing an EGR delete with a CCV reroute is the logical next step. Here's the reasoning:
The EGR system recirculates hot exhaust gases back into the intake to lower combustion temps and reduce NOx. The side effect is soot, carbon, and condensed exhaust residue coating the intake manifold, EGR cooler, and EGR valve over time. The CCV system compounds that problem by adding oil mist to the same intake stream. When you've got EGR gunk and CCV oil mist mixing inside the intake manifold, you get a nasty buildup that restricts flow and creates hot spots.
Delete the EGR, and you've removed one major source of intake contamination. Add a CCV reroute, and you've addressed the other. The result is an intake stream that's genuinely clean — just fresh air going to the turbo, just compressed air going to the combustion chambers. That's what your engine was designed to work with at peak efficiency.
Complete 6.7 Cummins delete kits for 2013–2024 Ram trucks include EGR, DPF, DEF, and CCV components in one package, so you're not piecing together parts from multiple sources. If you're shopping by platform, the full Ram Cummins delete kit collection covers every generation of the 6.7 from 2007.5 through current production.
For trucks where you want to address the exhaust side of the equation at the same time, pairing your CCV reroute and EGR delete with EGR delete kits makes for a clean, comprehensive build.
FAQs
Does a CCV reroute require a tune on the 6.7 Cummins?
In most cases, no. The CCV reroute is a mechanical change to the ventilation circuit, not the engine management system. Unlike an EGR delete or DPF delete, it doesn't trigger sensor faults that require ECU reprogramming. Some catch-can setups that loop back into the clean intake side are fully OEM-equivalent from the tune's perspective. If you're combining a CCV reroute with a full delete, your tune will be required for the other deleted systems, but the CCV reroute itself won't add to that requirement.
How often should I replace the factory CCV filter element?
Cummins recommends inspecting the CCV filter element at every other oil change and replacing it when it's saturated or shows restriction. In practice, many owners find the filter element is clogged well before that interval if the truck works hard. A clogged element increases crankcase pressure and pushes more oil past the separator, which is exactly the problem the reroute is designed to solve. If you're installing a reroute kit, inspect the valve cover filter element as part of the job.
Can I run a CCV reroute with a catch can and still pass emissions inspection?
Emissions requirements vary significantly by state. A catch-can setup that retains the CCV line and simply adds an oil separator is generally less likely to fail a visual inspection than a straight vent-to-atmosphere setup. However, any modification to the factory emissions-related systems can be flagged depending on your state's inspection protocol. Check your local requirements before making any modifications.
What's the best CCV reroute option for a 6.7 Cummins used for heavy towing?
For tow rigs running near capacity regularly, a catch-can setup with a quality coalescing element is the best combination of protection and cleanliness. High-load duty cycles produce more blow-by volume and more oil mist, so you want a separator that can handle the throughput without getting overwhelmed. Look for a catch can rated for diesel applications. Not all catch cans are built with the oil volume and pressure that a hard-working Cummins can produce.
Should I do the CCV reroute before or after a delete?
Either order works mechanically, but if you're planning a full delete, doing everything in one session saves time and avoids doing the intake area twice. The CCV reroute is one of the quicker parts of a complete delete build, so it makes sense to knock it out while you already have the intake and emissions hardware apart.
Ready to Clean Up Your Cummins?
If you're dealing with oily intercooler pipes, excess crankcase pressure, or you just want to set your 6.7 up the right way for heavy-duty use, a CCV reroute is one of the highest-value modifications you can make.
