Rick's Free Auto Repair Advice

Chrysler’s 3.5-liter engine oil sludge issues

Chrysler’s 3.5-liter engine has some problems with forming oil sludge. Oil sludge can destroy your engine.

The 3.5-liter V-6 engine is quickly developing a reputation as a problem child. It’s known for poor reliability caused by lubrication problems, oil sludge issues, leaking coolant, overheating, and low mileage failure. Some experts believe the engine suffers from poor design. Others blame owner neglect.

The engine is a variation of the very reliable 3.3-liter engine. The bores were enlarged and the compression ratio increased. The engine also has new cylinder heads and manifolds designed to work with the overhead cams. In addition, the intake system uses a dual throttle cross-ram intake with a tuning manifold valve. The engine was modified to accept a front mounted oil pump and timing belt to run the overhead cams. It was originally installed in the 1993-1997 LH vehicles (Intrepid, New Yorker, LHS, Eagle Visions, Prowler). Then the engine was redesigned, changed to an aluminum block and tweaked to provide up to 255HP.

Unfortunately, the engineers didn’t increase the size of the oil gallery passages or the coolant pipe that runs under the intake manifold. Another problem is the undersized PCV system. It doesn’t pull enough air through the crankcase, and that can result in oil sludging issues. The aluminum engine was used in 1998-2010 Chrysler 300, 300M, Challenger, Charger, Concorde, Intrepid, Pacifica, Prowler, and Sebring. The engine was discontinued in 2011 and replaced with the Pentastar V-6

Oil Sludging problems

This engine is famous for its oil sludging issues. Because the engine runs hot, it’s imperative that the PCV pull enough vapor out of the crankcase to prevent sludge formation. However, the PCV system is undersized. If the owner isn’t religious about changing oil every 3,000 miles, the heat and lack of ventilation can easily turn this engine into a sludgebox. Worse yet, as the oil breaks down and forms varnish, it restricts the already small oil gallery passages, causing oil starvation at crankshaft bearings. The result is premature bearing wear.

If these engines are not maintained, they can fail at around 80K miles.

You MUST ignore Chrysler’s advice of 7,500 oil change intervals and instead change oil every 3,000 miles. And, check for restricted PCV valve operation regularly. If you detect sludge accumulation, flush the engine immediately.

© 2012 Rick Muscoplat

Posted on by Rick Muscoplat



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