When it comes to high-performance engines, few can match the power and thrill of the 392 HEMI 6.4-liter engine. This legendary powerplant has found its way into various Dodge and Jeep vehicles, delivering a potent combination of horsepower and torque. However, even the most impressive engines can face issues, and one common problem that has plagued some 392 HEMI owners is MDS (Multi-Displacement System) failure. In this blog post, we’ll explore what MDS is, why it’s important, and the potential issues you may encounter with it in your 392 HEMI 6.4-liter engine.

What is the MDS System?

MDS, or Multi-Displacement System, is an innovative technology developed by Chrysler (now part of Stellantis) to improve fuel efficiency in their V8 engines. The 392 HEMI 6.4-liter engine is equipped with this system, which allows it to seamlessly transition between 8-cylinder and 4-cylinder modes, depending on driving conditions. When cruising at a steady speed, the engine can deactivate four of its eight cylinders to conserve fuel. When more power is needed, all eight cylinders come back to life, delivering the full might of the HEMI.

MDS Failure: What to Look Out For

While the MDS system is designed to enhance fuel efficiency, it can be a source of trouble for some 392 HEMI owners. Here are some common MDS failure issues to watch out for:

• Rough Idle — One of the early signs of MDS trouble is a rough or uneven idle. When the system fails to deactivate or reactivate cylinders properly, it can lead to a noticeable shake in the engine, especially when idling. This can be frustrating and concerning for drivers.

• Misfires — MDS issues can also manifest as misfires during acceleration. The engine may struggle to switch between 4-cylinder and 8-cylinder modes, causing a lack of power and performance hiccups.

• Check Engine Light — A malfunctioning MDS system can trigger the check engine light on your dashboard. Modern vehicles are equipped with sophisticated onboard diagnostics that can detect irregularities in the engine’s operation.

• Decreased Fuel Efficiency — Contrary to its intended purpose, a failing MDS system can actually reduce fuel efficiency. If the engine is stuck in 8-cylinder mode when it should be in 4-cylinder mode, it will consume more fuel than necessary.

Causes of MDS Failure

Understanding the potential causes of MDS failure can help you take preventive measures and address issues promptly. Some common reasons for MDS problems include:

Failure of the System Due to Oil Contamination

• Cause: Oil contamination due to improper maintenance, including not changing the oil, using contaminated oil, excessive crankcase pressure, coolant leaks, worn-out seals, improper installation of components (gaskets or filters), misalignment of parts during installation, and failure of related parts causing leakage into the oil pan.
• Symptoms: Oil leaks, engine noises (grinding or clunking), decreased power or torque, increased fuel consumption, elevated exhaust emissions.
• Solution: Replacement of affected parts (gaskets, filters, seals, etc.), cleaning coolant leaks, using good quality and clean oil, and following a regular service schedule.

The MDS Lifter Failure

• Cause: Lifter failure attributed to the MDS system’s implementation and oil contamination.
• Symptoms: Rattling engine noise, reduced power and torque, poor fuel economy, high emissions, engine stalling.
• Solution: Replacement of worn-out or damaged parts affected by oil contamination (filters, gaskets, seals, etc.), use of good quality and clean oil. Professional help is recommended, and in some cases, swapping stock parts with compatible non-MDS lifters and disabling MDS via an ECM flash may be an alternative.

Stuck Valve

• Cause: Valves getting stuck due to low oil pressure, clogged oil passages, or worn valve lifters.
• Symptoms: Strange engine noises, white smoke from the exhaust, possible internal engine damage.
• Solution: Depending on the cause, solutions may include increasing oil quantity or using higher-quality oil, clearing clogged passages with solvent and flush, and replacing worn valve lifters. Professional diagnosis and repair are essential to prevent further engine damage.

Fix Your HEMI 6.4 MDS Failure with Newparts.com!

The 392 HEMI 6.4-liter engine is a powerhouse of performance, but like any complex machine, it can encounter issues from time to time. MDS failure, while not extremely common, is one concern that some owners may face. By staying informed about the symptoms, causes, and solutions, you can ensure that your HEMI engine continues to deliver the thrilling performance it’s known for while maximizing fuel efficiency. Regular maintenance and prompt attention to any issues will go a long way in keeping your 392 HEMI running smoothly for years to come. If you’re looking for parts to fix your MDS issue, you’re in the right place! We offer a wide range of Mopar parts at excellent prices. Head over to our store, select your vehicle and find parts that are a guaranteed fit!