The AMG M157 5.5 BiTurbo V8 is a powerhouse — but once it fails, it fails HARD.
1. Common Failure Symptoms
- Rod knock
- Blue smoke
- Misfire under boost
- Timing chain rattle
- Oil pressure warning
- Rough idle
2. What Our Teardowns Show
2.1 Spun Rod Bearings
The most common M157 killer.
2.2 Oil Passage Restriction
Sludge or debris → wiped mains.
2.3 Timing Chain Stretch
Leading to:
- Poor performance
- Cam correlation errors
2.4 Piston Ring Land Cracking
Often from high boost + heat.
2.5 Turbo Seal Failure
Metal debris in oil → total engine failure.
3. Why These Failures Happen
- Long service intervals
- Small oil passages
- High cylinder pressures
- Poor PCV performance
- Heat cycling
4. Why You Need a Pre-Build Engine Lab Report
AMG engines are expensive
→ you need to know EXACTLY which parts are reusable.
We measure:
- Main/rod clearances
- Bore taper
- Deck warp
- Camshafts
- Turbo oil lines