The largest online repair guide library for every car

About us
Contact support
FAQ
Sign up
Sign in

2018 C300 M274 Engine Noise - Timing Chain or Turbo?

0

James R. · rep 0 · May 22, 4:22 AM · 1 replies · solved · Question

Hey everyone, I'm getting a bit worried about my 2018 Mercedes-Benz C300 (W205). It's got about 75k miles on it. Lately, I've noticed a rattling noise, especially on cold starts, that seems to come from the front of the engine. It sometimes sounds like a diesel, which is definitely not normal for a C300.

I've also felt a slight loss of power and heard a faint whistling sound under acceleration a few times. I'm concerned it might be related to the timing chain or even the turbocharger. I've read about issues with the M274 engine.

Has anyone else experienced similar symptoms with their C300? What was the diagnosis, and what kind of repair costs should I expect? I'm trying to figure out if this is a known issue or something more isolated.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:22 AM

0

ClearTheCode guidance (Mercedes-Benz · Buying & ownership)

Summary: For 2018 C300 M274 Engine Noise - Timing Chain or Turbo?, work through these steps on your 2016+ vehicle:

  1. Confirm the symptom — note when it happens (cold start, highway, after fuel fill, etc.).
  2. Scan codes — save all pending/stored DTCs; don't clear until you've recorded them.
  3. Check TSBs & recalls — look up your VIN for open campaigns and known fixes.
  4. Inspect the obvious — related fuses, connectors, fluid level, and recent repairs.
  5. Test the common fix — follow model-specific service procedures; one change at a time.
  6. Escalate if needed — burning smell, no brakes, overheating, or stalling in traffic → shop visit.

Owner reported: Hey everyone, I'm getting a bit worried about my 2018 Mercedes-Benz C300 (W205). It's got about 75k miles on it. Lately, I've noticed a rattling noise, especially on cold starts, that seems to come from the front of the engine. It sometimes sounds like a diesel, which is definitely not normal for a C300.

I've also felt a slight loss of power and heard a faint whistling sound under acceleration a …

This is educational guidance, not a substitute for hands-on diagnosis.

Menu

Help & account