engine

Oil Separator/PCV

for 1994–2007 Dodge Ram 2500 5.9L I6 Cummins Diesel · 4WD

Difficulty

Easy

Time

1.7 h

Tools

Steps

✓Fact-checked. Built from OLP's spec database, then independently fact-checked line by line with every correction applied. Master-tech sign-off by Chris Hackleman is queued. Cross-check torque values against the factory manual, and stop if anything looks unsafe. How our data is made.

This procedure replaces the crankcase breather filter assembly (oil separator/PCV system) on the 5.9L Cummins diesel engine to maintain proper crankcase ventilation and prevent oil contamination.

Warnings

⚠Perform this procedure on a cool engine. The valve cover and breather assembly retain heat and may cause burns.

ℹ️Some oil may drain from the breather assembly during removal. Have a catch pan ready.

ℹ️The 5.9L Cummins uses a filter-type breather system mounted on the valve cover, not a traditional PCV valve.

Tools required

10mm socket and ratchetEssential

13mm socket and ratchetEssential

Flathead screwdriverEssential

Needle-nose pliers

Shop towelsEssential

Catch pan or containerEssential

Wire brush

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Parts

Crankcase breather filter assembly × 1 — Mopar 68002433AA or equivalent
Crankcase breather mounting gasket × 1 — Use OEM specification
Breather hose clamps × 2 — As needed if damaged

As an Amazon Associate and Autel/ANCEL partner, OLP earns from qualifying purchases — how we link. This never changes the specs we publish.

Preparation

Ensure engine is cool to the touch
Park vehicle on level ground and engage parking brake
Open hood and secure with prop rod
Place catch pan or shop towels beneath the valve cover breather area to catch any oil drips
Inspect the breather assembly and hoses for visible damage or excessive oil accumulation

Procedure

1
Disconnect breather hoses
Locate the crankcase breather assembly on the valve cover. Note that the design and exact position differ between the 12-valve (1994-1998) and 24-valve (1998.5-2007) 5.9L Cummins engines; consult the correct diagram for your engine. Using a flathead screwdriver, loosen the hose clamps on both the intake tube connection and the crankcase vent hose. Carefully twist and pull the hoses off the breather assembly nipples. If hoses are stuck, gently work them side-to-side while pulling.
2
Remove breather assembly mounting bolts
Using the correct socket, remove the mounting bolts securing the breather assembly to the valve cover (verify exact bolt count and size for your engine before starting). Keep these bolts in a safe place as they will be reused. Note that some oil may be present around the mounting area.
3
Remove old breather assembly
Carefully lift the breather assembly straight up off the valve cover studs. Oil may drain from the assembly, so tilt it over your catch pan. Inspect the removed assembly for excessive sludge buildup or filter element damage to confirm replacement is needed.
4
Clean mounting surface
Remove the old gasket from the valve cover mounting surface. Use a wire brush or scraper if needed to remove any stuck gasket material or carbon buildup. Wipe the surface clean with shop towels. Inspect the valve cover area for any cracks or damage around the mounting holes.
5
Inspect crankcase vent passage
With the breather removed, look into the valve cover opening to check for excessive sludge or debris in the crankcase vent passage. If heavy buildup is present, this may indicate extended service intervals or blow-by issues that should be addressed.
6
Install new gasket
Position the new breather mounting gasket onto the valve cover. Align the gasket holes with the mounting studs or bolt holes. Ensure the gasket sits flat and fully contacts the valve cover surface all around.
7
Install new breather assembly
Place the new crankcase breather filter assembly onto the valve cover, aligning it with the mounting holes and ensuring it sits squarely on the gasket. The outlet nipples should face toward their respective hose connections.
8
Secure breather assembly
Thread in the mounting bolts by hand to prevent cross-threading. Once all bolts are hand-tight, use a 10mm socket to tighten them in a cross-pattern to ensure even seating. Tighten firmly but do not over-torque, as the valve cover can be damaged. Torque the mounting bolts to the manufacturer's specification for your engine (verify exact spec before tightening).
9
Reconnect breather hoses
Slide the crankcase vent hose and intake tube connection back onto the appropriate nipples of the breather assembly. Push each hose on firmly until it bottoms out on the nipple. Position the hose clamps over the hose-to-nipple connection point, approximately 1/4 inch from the hose end.
10
Secure hose clamps
Using a flathead screwdriver, tighten both hose clamps securely. Ensure clamps are positioned properly over the hose and nipple connection. Tug gently on each hose to verify secure attachment. Replace clamps if they are damaged or do not hold firmly.

Reassembly

Double-check that all hose connections are secure and clamps are properly tightened
Verify no tools or parts were left in the engine compartment
Wipe away any spilled oil from the valve cover and surrounding areas

Verification

Start the engine and allow it to idle for 2-3 minutes
Inspect the breather assembly and all hose connections for any signs of air leaks or oil seepage
Listen for any unusual hissing sounds that might indicate a vacuum leak at the breather connections
After a short test drive, recheck all connections while engine is still warm to ensure no leaks have developed
Monitor for reduced oil consumption and cleaner intake system over the next few hundred miles, which indicates proper breather function

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