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Mercedes-Benz · Known Issues

2021 Mercedes-Benz C-Class Problems: 1 Known Issue

2021 model year · 1,500+ owner reports · Updated September 2026

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Issue summary

According to Au7o's analysis of 1,500+ owner reports, the 2021 Mercedes-Benz C-Class has 1 documented issue. None of the listed issues is rated critical; this is not a complete reliability assessment. The most commonly reported issue is M274 Turbo Wastegate Rattle with 1,500 owner reports. Across all issues with published estimates, repair costs range from $400 to $2,500. DIY maintenance guides at au7o.io.

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In This Article

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All 1 Known Issue

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Community reported
1,500 owners

On the 2015-2021 Mercedes-Benz C-Class 2.0L M274 Turbo, the M274 2.0L turbo engine develops an audible wastegate rattle at idle and low RPM due to wear in the wastegate actuator linkage. While not immediately dangerous, it worsens over time and can eventually affect boost control.

This issue also affects: Mercedes-Benz CLA, Mercedes-Benz GLA, Mercedes-Benz GLE

Common Symptoms

  • Rattling noise at idle from turbo area
  • Rattle worsens in cold weather

How to Fix

Replace the turbocharger wastegate actuator or the complete turbo assembly if linkage is excessively worn. Some dealers adjust the wastegate arm as a temporary fix.

Owner tips & cautions

  • TipIf the rattle is mild and no boost codes are present, monitor it. Many owners live with the noise for years. Only replace if boost control is affected.
Typical repair cost:$400 - $2,500

Research This Issue

Based on 1,500 owner reports

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Community Reported
High Confidence1,500 owner reportsLast reported by owners Nov 2025Reviewed Mar 2026
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Other Mercedes-Benz Models

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Frequently Asked Questions

What are the most common Mercedes-Benz C-Class problems?

According to Au7o's analysis of 1,500+ owner reports, the 2021 Mercedes-Benz C-Class has 1 documented issue. The documented issue is: M274 Turbo Wastegate Rattle. None are rated critical, but regular maintenance is recommended.

Is the Mercedes-Benz C-Class reliable?

The 2021 Mercedes-Benz C-Class has 1 known issue documented across 1,500+ owner reports. None of the matching records is rated critical; this is not a complete reliability assessment. Regular maintenance following the manufacturer's schedule helps prevent many common problems.

How much does it cost to fix common Mercedes-Benz C-Class problems?

Repair costs for known Mercedes-Benz C-Class issues range from $400 to $2,500, depending on the specific problem and whether you choose DIY or professional repair. Au7o provides step-by-step DIY maintenance guides that can help reduce repair costs.

What is the 2015-2021 Mercedes-Benz C-Class M274 Turbo Wastegate Rattle?

The M274 2.0L turbo engine develops an audible wastegate rattle at idle and low RPM due to wear in the wastegate actuator linkage. While not immediately dangerous, it worsens over time and can eventually affect boost control. Repairs typically run $400-$2,500. Severity: medium.

Content on this page was compiled with AI assistance using NHTSA complaints, TSBs, owner reports, and public automotive data. While we strive for accuracy, this information may contain errors. Always verify repair procedures and specifications with your vehicle's service manual or a qualified mechanic.

Data sourced from 1,500+ owner reports, NHTSA recalls, TSBs, and automotive forums.