Mercedes-Benz SL R232

The M139 is the logical development of the M133 and surpasses it in every respect: more power, better thermal management through an improved cooling concept, combined direct and port injection to fight intake valve carbon build-up. As a young engine with limited long-term data it is considered robust so far. Isolated reports of coolant sensor issues and water pump failures at high speeds. Tuning potential is enormous, but fuel supply must be upgraded at higher power levels.

• !! Turbocharger Stress Under Extreme Use from 100,000 km

  The world's most powerful series-production four-cylinder at 421 hp subjects its turbocharger to extreme stress. Without adequate cool-down periods after full-load operation, premature bearing wear is likely.

  Symptoms: Whistling at high load, oil mist in intake tract, power drop in heat
  2,500–5,000 $
  Ad Turbocharger M139Turbocharger M139 AMGTurbo M139 replacement
• !! Turbocharger Shaft Seal Leaking from 80,000 km

  The high-performance turbocharger on the M139 can push oil into the intake tract due to excessive shaft play. Early vehicles were subject to a recall for turbocharger bearing defects.

  Symptoms: Oil consumption without visible leaks, smoke cloud on cold start, power drop under high load
  2,000–5,000 $
  Ad Turbocharger M139BorgWarner turbocharger M139Turbo M139 BorgWarner
• !! Overheating After Spirited Driving from 60,000 km

  The M139 cooling system is designed at its limits. After extended high-load phases coolant temperature can reach critical values, especially in warm weather.

  Symptoms: Coolant temperature warning after spirited driving, restricted engine power through thermal management
  800–2,500 $
  Ad Water pump M139Cooling M139 AMGA1332001900 thermostat M139

+ 3 more engine weaknesses + vehicle weaknesses

The M177 is AMG's most widely used V8 biturbo today and is considered technically mature and long-lived. The hot-V turbocharger arrangement delivers spontaneous response with barely perceptible lag. Weaknesses are manageable: wastegate rattle in cold weather, ignition coil recall for early 2015 model years, valve cover gaskets with age. Regular oil changes with attention to oil quality deliver a very robust engine. In direct comparison with the M156 less emotional, but significantly more reliable and efficient.

• !! MCT Gearbox — Clutch Wears in City Traffic from 60,000 km

  The MCT Speedshift gearbox (wet launch clutch instead of torque converter) wears the clutch significantly faster in frequent stop-and-go. Clutch replacement requires gearbox removal.

  Symptoms: Judder on pull-away, clutch slip at full load, gearbox warning message, delayed engagement from standstill
  3,000–6,000 $
  Ad MCT clutch AMG C63 W205Speedshift MCT clutch kitA2052500200 MCT clutch
• !! Camshaft Adjuster Solenoid Draws Oil into Wiring Harness from 70,000 km

  Identical issue to the M176/M278: the solenoid leaks, oil migrates by capillary action through the wiring harness. On AMG vehicles this is even more frequent due to higher oil temperatures.

  Symptoms: Cold-start rattle, camshaft adjuster fault code, oil traces on connector, potential ECU consequential damage
  500–3,000 $
  Ad Camshaft adjuster M177 AMGOil stop ring M177 wiring harnessA1779050100 solenoid
• !! Timing chain guide failure from 100,000 km

  At higher mileage the plastic timing chain guide rails can fracture. Debris enters the oil sump and can cause secondary damage. Repair costs €4,000–8,000.

  Symptoms: Tek-tek-tek noise on cold start that disappears after a few minutes. Later: extended start times, knocking from engine bay
  4,000–8,000 $

+ 6 more engine weaknesses + vehicle weaknesses

The M177 is AMG's most widely used V8 biturbo today and is considered technically mature and long-lived. The hot-V turbocharger arrangement delivers spontaneous response with barely perceptible lag. Weaknesses are manageable: wastegate rattle in cold weather, ignition coil recall for early 2015 model years, valve cover gaskets with age. Regular oil changes with attention to oil quality deliver a very robust engine. In direct comparison with the M156 less emotional, but significantly more reliable and efficient.

• !! MCT Gearbox — Clutch Wears in City Traffic from 60,000 km

  The MCT Speedshift gearbox (wet launch clutch instead of torque converter) wears the clutch significantly faster in frequent stop-and-go. Clutch replacement requires gearbox removal.

  Symptoms: Judder on pull-away, clutch slip at full load, gearbox warning message, delayed engagement from standstill
  3,000–6,000 $
  Ad MCT clutch AMG C63 W205Speedshift MCT clutch kitA2052500200 MCT clutch
• !! Camshaft Adjuster Solenoid Draws Oil into Wiring Harness from 70,000 km

  Identical issue to the M176/M278: the solenoid leaks, oil migrates by capillary action through the wiring harness. On AMG vehicles this is even more frequent due to higher oil temperatures.

  Symptoms: Cold-start rattle, camshaft adjuster fault code, oil traces on connector, potential ECU consequential damage
  500–3,000 $
  Ad Camshaft adjuster M177 AMGOil stop ring M177 wiring harnessA1779050100 solenoid
• !! Timing chain guide failure from 100,000 km

  At higher mileage the plastic timing chain guide rails can fracture. Debris enters the oil sump and can cause secondary damage. Repair costs €4,000–8,000.

  Symptoms: Tek-tek-tek noise on cold start that disappears after a few minutes. Later: extended start times, knocking from engine bay
  4,000–8,000 $

+ 6 more engine weaknesses + vehicle weaknesses