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2016 C300 M274 Engine Oil Leak & Rough Idle - Check Engine Light

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Mark S. · rep 0 · May 25, 3:09 AM · 1 replies · solved · Question

Vehicle: 2016 Mercedes-Benz C300 Base

Hey everyone, I'm hoping for some advice here. My 2016 Mercedes-Benz C300 (W205) with the M274 engine has developed an oil leak that seems to be coming from the front of the engine, possibly around the timing cover or cam adjusters. I'm also experiencing a slightly rough idle, and the check engine light has come on intermittently.

I scanned it with an OBD-II reader and got codes P0016 and P0017, which point to crankshaft/camshaft position correlation issues. Could these be related to the oil leak, perhaps a failing cam adjuster or a stretched timing chain? The car has about 85,000 miles on it.

What's the typical repair cost for something like this? Is this a known issue for this model year and engine? Any insights on what I should be looking for or asking my mechanic would be greatly appreciated. Thanks!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 3:09 AM

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ClearTheCode admin answer:

The issues you're describing with your 2016 C300 are unfortunately common for the M274 engine, particularly the oil leaks and camshaft position correlation codes. Here's a breakdown:

  1. Likely Cause of Oil Leak & Codes: The P0016 and P0017 codes, combined with an oil leak at the front of the engine, strongly suggest issues with the camshaft adjusters (also known as cam actuators or phasers) or the seals around them. These adjusters are crucial for variable valve timing. Over time, their internal seals can fail, leading to oil leaks, and the adjusters themselves can wear, causing incorrect timing and triggering these codes. A stretched timing chain is less common but possible, especially if the adjusters have been failing for a while.

  2. Why it Happens: The M274 engine's cam adjusters have been known to fail due to material degradation of internal components or seals. The oil leak often originates from the adjuster housing or the front timing cover gasket, which can also degrade.

  3. When to See a Shop: You should see a qualified Mercedes-Benz specialist as soon as possible. Driving with these issues can lead to:

    • Further engine damage if oil levels drop too low.
    • Reduced fuel economy and performance.
    • Potential catastrophic engine failure if the timing chain or adjusters completely seize or fail.

  4. What to Expect at the Shop:

    • Diagnosis: The shop will perform a thorough diagnostic, including checking oil pressure, inspecting the leak source, and potentially using Mercedes-Benz specific diagnostic tools to confirm cam adjuster operation and timing chain stretch.
    • Repair: The repair typically involves replacing the faulty camshaft adjusters and the associated seals and gaskets. In some cases, if the timing chain is stretched beyond specification, it may also need replacement. This is a labor-intensive job as it often requires significant disassembly of the front of the engine.
    • Parts: Ensure genuine Mercedes-Benz parts or high-quality OEM equivalents are used for critical components like cam adjusters.

  5. Cost Expectation: Repair costs can vary significantly based on your location and the specific components needing replacement. For cam adjusters and gaskets, you might be looking at $2,000 - $4,000+. If the timing chain also needs replacement, the cost could be higher. Get a detailed quote before authorizing any work.

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