If you own a 3.0 EcoDiesel, the VM Motori V6 in Ram 1500s, Jeep Grand Cherokees, Wranglers, and Gladiators, and you keep finding oil down the back of the engine or smell it burning, do not jump straight to a rear main seal. The far more common culprit on these engines is the oil filter housing and its cooler module sitting in the valley. It cracks and its seals fail, and the oil it weeps runs down the back of the block in a way that mimics a much bigger job.
What the oil filter housing does on the EcoDiesel
The EcoDiesel mounts its oil filter housing in the valley of the V6, and that housing also integrates the oil cooler and its coolant passages. It is a compact module handling both engine oil and coolant, sealed by a set of O-rings and gaskets, with a cartridge-style oil filter on top. Because it lives in the valley under the intake and turbo plumbing, a leak there does not drip where you can see it. It runs down the back of the engine and shows up low, which is exactly why people misread it as a rear main leak.
Two things fail here. The housing itself, which on these engines is a composite/plastic construction, can crack or distort from heat cycling. And the O-rings and gaskets that seal the oil and coolant passages harden and leak. Either one puts oil in the valley.
Symptoms of a failing oil filter housing
- Oil weeping down the back of the engine and pooling low, often mistaken for the rear main.
- A persistent oil smell and light smoke as oil drips onto hot exhaust components.
- Slow oil consumption with no obvious external drip, because the leak is hidden in the valley.
- Oil residue around the filter cap or the base of the housing once you get up top and look.
- Coolant weeping or cross-contamination in worse cases, since the module carries coolant too, so inspect for both fluids.
Because the leak hides under the intake and turbo plumbing, confirmation usually means getting the top of the engine cleaned off, running it, and tracing the fresh oil back to the housing rather than guessing from the puddle location.
How to diagnose it
Clean the valley and the back of the engine thoroughly so any new leak is obvious. Run the engine to temperature and look for fresh oil originating at the oil filter housing, its base gasket, or the O-rings, rather than at the true rear main behind the flywheel. A borescope or a mirror helps see the back side of the housing. Check the coolant as well, since the module's coolant passages can seep or cross into the oil path. If the fresh oil trail starts at the housing, you have your answer, and you have saved yourself from pulling a transmission to chase a seal that was never the problem.
The fix, and doing it once
Replace the oil filter housing with an updated unit and a full set of fresh O-rings and gaskets. Mopar revised these housings, so fitting a current-design replacement rather than reusing an old cracked one is the whole point. While you are in there:
- Replace every O-ring and gasket the module uses, not just the obvious one.
- Inspect and service the oil cooler seals at the same time, since they share the same environment and age together. This engine is also known for oil cooler and EGR cooler issues, so address them together while the top end is open.
- Use fresh coolant if you disturbed the coolant passages, and burp the system.
- Fit a new cartridge oil filter and change the oil, since you will lose some during the job.
Do not reuse hardened seals or an old cracked housing. This is a job you want to do once.
Parts you'll need
- Updated oil filter housing / oil cooler module
- Complete O-ring and gasket set for the housing
- Oil cooler seals if you service the cooler at the same time
- Cartridge oil filter and fresh engine oil
- Correct-spec coolant if the coolant passages were opened
Housing gaskets, O-rings, and seal kits are organized by engine in our diesel gaskets and seals collection, and the rest of the platform lives in the 3.0L EcoDiesel parts collection. Organized by engine, confirm fitment for your application.
FAQ
How do I know it is the housing and not the rear main seal? Clean everything, run it, and trace the fresh oil to its origin. Housing leaks start up in the valley and run down the back; a rear main leak originates behind the flywheel. The housing is far more common on this engine.
Should I replace the oil cooler at the same time? It is smart. The cooler seals live in the same hot valley and age with the housing. Doing both while it is open saves you a second teardown.
Is the replacement housing any better than the original? The updated design addresses the cracking that plagued earlier units, so fitting a current housing rather than reusing an old one is the fix, not a band-aid.
Where we land
An EcoDiesel that leaks oil down the back of the engine is usually telling you the valley oil filter housing has cracked or its seals have failed, not that the rear main is gone. Clean it, trace the leak to the source, and replace the housing with an updated unit and fresh seals, servicing the oil cooler while you are in there. Do it right and the leak, and the burning-oil smell, are gone.
Shop 3.0L EcoDiesel diesel parts at coredieselparts.com. Free shipping over $70, ships fast.
Related guides: - 3.0 EcoDiesel EGR Cooler and Oil Cooler Problems - Diesel Oil Change Intervals and Choosing the Right Oil Filter