The 2020 Chrysler 300 sits on the venerable LX platform's final evolution — solid bones but showing age in its transmission cooling and specific Hemi weaknesses. The 3.6L Pentastar is generally reliable; the 5.7L and 6.4L Hemi variants carry cylinder deactivation (MDS) issues that plague many owners.
Transmission Oil Cooler Failure (ZF 8-Speed)
Common · high severityTypical onset: 60,000-90,000 mi
Symptoms: Pink or milky transmission fluid (coolant mixing), Transmission slipping or delayed shifts, Check engine light with P0741 or P0868 codes, Engine overheating in severe cases
Fix: Replace internal transmission cooler and flush both cooling system and transmission. If caught late, trans rebuild required. 4-6 hours labor for cooler alone, 12-18 hours if trans damaged.
Estimated cost: $800-1,200 (cooler only), $3,500-5,500 (with trans rebuild)
Hemi MDS Lifter and Camshaft Failure
Occasional · high severityTypical onset: 70,000-120,000 mi
Symptoms: Ticking or tapping noise at idle, worsens when warm, Check engine light with misfire codes (P0300-P0308), Loss of power, rough idle, Metal shavings in oil
Fix: Replace failed lifters, camshaft, and often rocker arms on affected bank. Requires heads-off work. 14-18 hours labor for single bank, 22-28 hours both banks.
Estimated cost: $3,200-4,800 (one bank), $5,500-7,500 (both banks)
Transmission Mount Collapse
Common · medium severityTypical onset: 50,000-80,000 mi
Symptoms: Clunking when shifting from Park to Drive, Vibration at idle in gear, Excessive drivetrain movement felt in cabin
Fix: Replace transmission crossmember mount. Simple job but requires trans support. 1.5-2 hours labor.
Estimated cost: $250-400
Fuel Pump and Filter Assembly Failure (Hemi)
Occasional · high severityTypical onset: 80,000-110,000 mi
Symptoms: No-start or extended cranking when hot, Loss of power under load or acceleration, Sputtering at highway speeds, P0087 low fuel pressure code
Fix: Replace in-tank fuel pump module. Tank must be dropped. 3-4 hours labor.
Estimated cost: $800-1,200
Water Pump Weep (3.6L Pentastar)
Occasional · medium severityTypical onset: 80,000-120,000 mi
Symptoms: Coolant seepage from timing cover area, Sweet smell from engine bay, Slow coolant loss over weeks, Occasional overheating if ignored
Fix: Water pump is timing-chain-driven, internal to front cover. Requires timing cover removal, new chains/guides recommended while in there. 6-8 hours labor.
Estimated cost: $1,200-1,800
Rear Differential Pinion Seal Leak
Occasional · low severityTypical onset: 60,000-100,000 mi
Symptoms: Gear oil drips on driveway from rear, Visible wetness at pinion flange, Low diff fluid on check (can cause whine or damage)
Fix: Replace pinion seal, sometimes requires pinion bearing preload reset. 2-3 hours labor.
Estimated cost: $350-550
EVAP Purge Valve and Leak Detection Pump Faults
Common · low severitySymptoms: Check engine light with P0442, P0455, P0456 EVAP codes, Failed emissions test, Occasional rough idle or stalling (purge valve stuck open)
Fix: Replace purge valve or leak detection pump. Usually purge valve on intake manifold. 0.5-1 hour labor each.
Estimated cost: $150-300
Buy the 3.6L V6 without hesitation; avoid high-mileage Hemis unless MDS lifters and cam have already been addressed or you're prepared for a $5K+ engine job.
AI-assisted summary drawn from NHTSA recall data, our labor-times database, and platform knowledge. Not a substitute for a pre-purchase inspection on a specific vehicle.