The crankcase filter traps oil mist before it enters your engine's air intake

The crankcase filter on a 6.7 Cummins diesel sits between the engine's crankcase ventilation system and the intake manifold. As your engine runs, pressure builds inside the crankcase and forces out gases mixed with fine oil particles. The crankcase filter catches those oil droplets so they do not get sucked into the intake and burned in the combustion chamber. Without it, oil accumulates in the intake, fouls spark plugs or glow plugs, and degrades fuel economy.

This is different from your main engine air filter or oil filter. The crankcase filter is smaller, sits in a different location, and handles a specific job: keeping oil mist out of the air your engine breathes. On the 6.7 Cummins, it is typically mounted on or near the valve cover.

Key Takeaways

  • The crankcase filter prevents oil mist from entering the intake manifold, which would foul combustion and reduce engine performance.
  • Replacement intervals vary by driving conditions, but most owners change it every 15,000 to 25,000 miles or once a year, whichever comes first.
  • A clogged crankcase filter increases crankcase pressure, which can force oil past seals and cause leaks around the valve cover or turbo.
  • The part itself costs between $30 and $80 depending on the supplier, and installation takes 15 to 30 minutes with basic hand tools.
  • Neglecting replacement can lead to intake carbon buildup, rough idle, and reduced fuel economy over time.

Where the crankcase filter sits on a 6.7 Cummins

On most 6.7 Cummins engines, the crankcase filter is mounted on the driver's side of the engine, typically on or near the valve cover. Some models have it integrated into a breather assembly that connects directly to the intake manifold. The exact location depends on your model year and whether you have a stock or modified intake setup.

To locate yours, open the hood and look for a cylindrical or cartridge-style filter housing on the top of the engine. It will have a hose or tube running to the intake manifold. If you cannot find it visually, your owner's manual or a service diagram specific to your year will show the exact position.

Replacement intervals and warning signs

Most 6.7 Cummins owners replace the crankcase filter every 15,000 to 25,000 miles under normal driving, or once per year if you drive fewer miles. Heavy-duty use—towing, idling for long periods, or driving in dusty conditions—shortens that interval. Some owners on forums report changing theirs every 10,000 miles if they tow regularly.

Watch for these signs that replacement is overdue: increased crankcase pressure (you may notice oil seeping from the valve cover gasket or turbo seals), rough idle, a slight loss of power, or a hissing sound from the breather system. If you see oil residue around the intake manifold or notice a burnt-oil smell, the filter may be clogged and forcing oil past its capacity.

How to replace the crankcase filter yourself

Replacement is straightforward and requires only basic tools: a wrench or socket set, a drain pan (optional, to catch any residual oil), and the replacement filter. The process takes 15 to 30 minutes.

First, locate the filter housing and disconnect the hoses running to and from it. Some housings are held by a single bolt or clamp; others screw directly into the valve cover. Remove the old filter cartridge and inspect the housing for debris or oil buildup. Wipe the inside clean with a lint-free cloth. Install the new filter, reconnect the hoses, and tighten any bolts or clamps. Start the engine and check for leaks around the connections. If you see oil dripping, tighten the fittings slightly and recheck.

Cost and parts availability

A replacement crankcase filter for the 6.7 Cummins costs between $30 and $80 depending on the brand and supplier. OEM Cummins filters tend toward the higher end; aftermarket options from brands like Mopar or third-party manufacturers are usually cheaper. Many diesel shops and online retailers stock them, and availability is generally good because the 6.7 Cummins is a common engine in Dodge Ram trucks.

If you have the filter replaced at a shop, expect labor charges of $75 to $150 on top of the part cost. Many independent diesel shops charge less than dealerships for this routine maintenance.

What happens if you ignore a clogged crankcase filter

A clogged crankcase filter forces pressure to build inside the crankcase. That pressure has to go somewhere, so it pushes oil past seals and gaskets—typically around the valve cover, turbo seals, or the oil pan gasket. You will see slow oil leaks that worsen over time and can eventually lead to low oil levels if not caught.

The excess pressure also forces oil mist into the intake manifold despite the clogged filter, which deposits carbon on intake valves and in the combustion chamber. This causes rough idle, hesitation during acceleration, and reduced fuel economy. Over months of neglect, you may need intake cleaning or valve work to restore performance. Replacing the filter on schedule costs $30 to $80 and takes 30 minutes; ignoring it can cost hundreds in repairs.

Frequently Asked Questions

Can I drive with a clogged crankcase filter?

Yes, but you should not. A clogged filter increases crankcase pressure, which forces oil past seals and into the intake. This causes slow leaks and carbon buildup. Replacement takes 30 minutes and costs $30 to $80, so it is worth doing before problems develop.

Is the crankcase filter the same as the PCV valve?

No. The PCV (positive crankcase ventilation) valve regulates pressure and flow from the crankcase; the crankcase filter traps oil mist before it reaches the intake. Some systems have both. Check your engine diagram to see which components your 6.7 has.

What if I replace the filter and still see oil leaks?

The leaks may be from a separate issue—a worn valve cover gasket, turbo seal, or oil pan gasket. A new crankcase filter stops pressure from building, but it does not repair existing damage. If leaks continue after replacement, have a mechanic inspect the seals.

Do I need to change the crankcase filter if I do not tow?

Yes. Even light driving generates crankcase pressure and oil mist. Most owners change it annually or every 15,000 to 25,000 miles regardless of use. Light driving may extend the interval slightly, but skipping it entirely will eventually cause problems.