Knowledge base
Common Faults
Practical guides on Mercedes servicing, diagnostics, common faults and ownership — written by the technicians doing the work.
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faults
Mercedes Brake Pad Wear Sensor: Why the Light Won't Clear and How to Fix It Properly
Replaced your Mercedes brake pads but the warning light will not go out? This is one of the most common post-repair complaints we see. Here is exactly why it happens…
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faults
Mercedes OM651 Head Gasket Failure: Symptoms, Causes & What It Actually Costs to Repair
The OM651 diesel is known for head gasket failure, particularly on higher-mileage examples. Here is how to diagnose it correctly — because it is often misdiagnosed as an EGR cooler…
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faults
Mercedes M271 Timing Chain Stretch: The Complete Guide to Diagnosis, Repair & Cost
The M271 timing chain problem is the most-discussed fault on the 1.8 Kompressor engine. Here is everything you need to know: how to spot it, how to confirm it, what…
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faults
Mercedes M272/M273 Balance Shaft Failure: How to Check If Your Engine Is Affected
The M272/M273 balance shaft issue is one of the most expensive known faults on any modern Mercedes engine. Here is how to check if your car is affected before you…
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Mercedes Blocked DPF: Warning Signs, Cleaning vs Replacement & Real London Costs
A blocked DPF on a modern Mercedes diesel can trigger limp mode and costs hundreds — sometimes thousands — to resolve. Here is how to spot it early, what the…
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faults
Mercedes AdBlue System: How It Works, What Fails, and How to Avoid the Dreaded Countdown
The AdBlue countdown warning is one of the most stressful experiences for a modern Mercedes diesel owner. Here is exactly what causes it, how the SCR system works, and what…
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faults
Mercedes OM642 V6 Diesel: The Definitive Fault List Every Owner Needs
The OM642 V6 diesel powers the E350, C350, ML350, GL350 and S350. It is fundamentally strong but has five well-known weak points that every owner should know about before the…
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faults
Mercedes C-Class W204 Common Faults: The 8 Problems Every Owner Should Know About
The W204 is widely regarded as one of the most reliable modern Mercedes — but it has a handful of well-documented faults that every owner should budget for. Here are…
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faults
Mercedes C-Class W205 Common Faults: A 2026 Owner's Guide
The W205 C-Class improved on the W204 in almost every way — but it introduced new electronic complexity and an AdBlue system that has become its most common and expensive…
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