The Chrysler 300 with its 5.7L Hemi V8 offers big-car luxury with muscle car performance. But that smooth-running Hemi can develop an unwelcome soundtrack—a persistent ticking noise that many owners describe as coming from under the hood. This tick often points to issues with the Multi-Displacement System (MDS) lifters, a known concern in modern Hemis.
The MDS System Explained
The Multi-Displacement System allows the 5.7L Hemi to deactivate four cylinders during light-load cruising, effectively turning your V8 into a V4 for better fuel economy. Special lifters on cylinders 1, 4, 6, and 7 contain mechanisms that lock and unlock to control valve operation. When these lifters fail, they often announce it with a tick.
Identifying Lifter Tick
Lifter tick has distinctive characteristics:
- Rhythmic ticking that follows engine speed
- Often loudest at idle and light throttle
- May improve or worsen when engine warms up
- Sound typically comes from upper engine area
- Often described as mechanical, metallic tick
Common Causes
MDS Lifter Failure
The complex MDS lifters contain more internal components than standard lifters. The locking mechanism, needle bearings, and internal springs can wear or fail. Failed MDS lifters may collapse, stick, or operate erratically.
Oil Quality and Pressure Issues
MDS lifters are highly sensitive to oil quality and pressure. Degraded oil, wrong viscosity, or low pressure can cause lifters to malfunction or fail to pump up properly.
Rocker Arm Wear
Worn rocker arms affect valve train geometry, creating tick and potentially causing lifter problems. The roller tip can wear, creating play and noise.
Oil Flow Restrictions
Clogged oil passages in the cylinder head can starve lifters of lubrication, causing tick and accelerating wear.
Diagnostic Steps
- Verify oil level and condition: Check that oil is at proper level and not severely degraded.
- Cold vs. warm tick: A tick that disappears when warm may be minor; one that persists or worsens is more concerning.
- Locate the tick: Use a mechanics stethoscope to identify which bank or cylinder the tick originates from.
- Check for codes: Severe lifter issues often set misfire codes on affected cylinders.
- Oil pressure test: Verify oil pressure meets specifications at idle and at 2,000 RPM.
Repair Options
Live With It
Minor tick that doesn't worsen may not require immediate action. Regular oil changes with quality synthetic oil and monitoring are reasonable if the tick isn't severe.
MDS Disable (Software)
Disabling MDS through tuning prevents the constant cycling that contributes to lifter wear. This doesn't fix already-damaged lifters but may slow further deterioration.
Lifter Replacement
Replacing failed lifters addresses the immediate problem. Replacing all MDS lifters is typically recommended since others may be near failure. Cost: $2,500-$4,000.
MDS Delete Conversion
The most comprehensive solution replaces all MDS lifters with standard lifters and installs a non-MDS camshaft. This eliminates the failure-prone components entirely. Cost: $3,500-$5,000.
Prevention
- Use quality full synthetic oil meeting MS-6395 specification
- Change oil every 5,000 miles—don't push extended intervals
- Allow engine to warm before spirited driving
- Consider MDS disable software if tick develops early
- Address tick early before lifter failure causes additional damage