M278 Timing Chain Stretch (Twin-Turbo V8)
The M278 4.7L twin-turbo V8 engine, found in many 2012-2018 Mercedes models, uses timing chains that are prone to elongation over time. The chains are located at the rear of the engine (between the engine and transmission), making this one of the most labor-intensive timing chain jobs in the automotive world. Chain stretch causes timing deviation, which triggers camshaft correlation fault codes and can lead to catastrophic engine damage if the chain jumps a tooth.
Which models are at risk.
Warning signs to watch for.
Timing chain rattle on cold start, especially noticeable from the rear of the engine
Check engine light with P0016, P0017, P0018, or P0019 camshaft correlation codes
Rough or uneven idle
Loss of power or hesitation under acceleration
Engine misfires under load
Increased fuel consumption
Why this happens.
Timing chain links elongate over time due to the high torque output of the twin-turbo V8
Chain guide rails and tensioners wear, allowing additional chain slack
Oil quality and change intervals significantly affect chain and tensioner longevity
The rear-mounted chain design makes the chains run hotter than front-mounted designs
High-mileage vehicles and those subjected to aggressive driving wear chains faster
How we diagnose it.
- 01
Scan for camshaft position correlation codes (P0016-P0019) using Star Diagnostic
- 02
Use the Star Diagnostic timing chain measurement function to quantify chain elongation
- 03
Monitor camshaft adjuster angles at idle — excessive deviation indicates chain slack
- 04
Listen for chain rattle with a stethoscope at the rear of the engine (transmission bellhousing area)
- 05
Check for metal particles in the engine oil during an oil change — indicates chain and guide wear
How we fix it.
Complete timing chain replacement (engine in vehicle, transmission removed)
Thorough repair with access to all chains, guides, and tensioners; avoids engine removal
Requires transmission removal; 20-30 hours labor; still a major job
Complete timing chain replacement (engine removed)
Best access for complete chain, guide, and tensioner replacement; allows inspection of all engine seals
Highest labor cost; longest downtime (3-5 days); requires engine hoist and specialized tooling
Engine replacement with remanufactured unit
Fully remanufactured engine with all new chains, seals, and bearings; warranty on replacement
Highest total cost; may not be justifiable on an older or higher-mileage vehicle
Keep it from happening.
Change oil every 7,500 miles with MB 229.5 specification oil — do not follow the extended 10,000+ mile interval
Use a quality oil filter (genuine Mercedes, MANN, or Hengst)
Avoid excessive cold-start idling — get the oil warm before spirited driving
Listen for any new engine noises and address immediately
Consider proactive chain replacement around 100,000-120,000 miles on well-maintained vehicles
Common questions.
Why are the timing chains at the rear of the M278 engine?
Mercedes mounted the timing chains at the rear (transmission side) of the M278 to optimize the front of the engine for the twin turbocharger plumbing. This packaging decision makes the engine compartment more compact but makes timing chain service vastly more complex and expensive than a traditional front-mounted chain design.
How long do M278 timing chains last?
With proper oil maintenance, M278 timing chains typically last 100,000-150,000 miles. However, extended oil change intervals, aggressive driving, and poor oil quality can accelerate wear. Some owners have reported chain stretch as early as 60,000-80,000 miles with poor maintenance.
Can the chain skip a tooth?
Yes. If the chain stretches enough to exceed the tensioner travel, it can skip one or more teeth on the camshaft sprockets. This changes the valve timing dramatically and can cause valve-to-piston contact, bending the valves and potentially scoring the cylinder walls. This turns a timing chain job into a complete engine rebuild or replacement.
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Learn more →Let’s take care of your Mercedes.
Give us a call. We’ll diagnose the problem with factory tooling and give you an honest assessment before any work begins.
7492 Slater Ave, Huntington Beach, CA 92647 · Mon–Fri 8:00am–5:00pm