Wrangler Oil Cooler Housing Failure (3.6L)

Why the Plastic Housing Fails

The 3.6L Pentastar has a combined oil filter housing and oil cooler assembly made entirely of plastic. This part sits on top of the engine underneath the intake manifold where it's exposed to extreme heat from the engine below. Over time the plastic becomes brittle from constant heat cycling through thousands of warm-up and cool-down cycles. Eventually hairline cracks develop that grow until the housing fails. When it finally lets go, you can lose oil pressure and coolant at the same time because both fluids route through adjacent internal passages that share a common wall.

This failure is well documented on the Pentastar and is one of the most common oil leak sources on 2012 and newer Wranglers. It is not a matter of if the plastic housing will fail, but when. Engines used for towing or off-roading tend to fail sooner due to higher operating temperatures.

Early Warning Signs

The first sign of trouble is usually oil leaking from the top of the engine. The oil runs down both sides of the engine block, and you may notice the smell of burning oil as it drips onto hot exhaust manifolds. Another indicator is losing coolant without any visible external leak from hoses or the radiator. A low coolant level that keeps coming back is a strong clue that the oil cooler housing may be the source.

The most serious symptom is milky or frothy oil on the dipstick. This means the internal wall has failed completely and coolant is mixing with the engine oil. If you see milky oil, stop driving immediately. Coolant in the oil destroys main bearings, rod bearings, and cam bearings very quickly — often within just a few miles. A full engine replacement may be needed at that point.

The Permanent Fix — Aluminum Housing

Aftermarket companies have responded with a permanent fix. Dorman makes an aluminum replacement housing that eliminates the plastic cracking problem permanently. The aluminum housing costs about $200, which is about $50 more than the OEM plastic part that will eventually fail again. The aluminum upgrade is the smart choice if you plan to keep your Wrangler long term, and it dissipates heat better than plastic.

Replacement requires removing the intake manifold to access the housing. This is about a 3 to 4 hour job at home with basic hand tools and a torque wrench. If you pay a shop, expect $600 to $1,000 for parts and labor. While you have the intake manifold off, replace the intake manifold gaskets and clean any carbon deposits from the back of the intake valves.

Preventative Replacement

Many experienced Pentastar owners replace the oil cooler housing preventatively when they have the intake manifold off for any other reason. This saves the labor cost of doing the job twice and gives peace of mind that the most common oil leak on the Pentastar has been addressed permanently with a part that will never crack.

Bottom Line

If you own a 3.6L Wrangler, replace the plastic oil cooler housing with a Dorman aluminum unit before it fails. Watch for oil on top of the engine and check your dipstick for coolant contamination. This is a one-time fix that eliminates the most common oil leak on the Pentastar permanently.

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