The 2008 S65 AMG pairs a hand-built 6.0L twin-turbo V12 (M275) with Mercedes' 5-speed 722.6 transmission in a luxury flagship body. While the platform itself is solid, the engine has well-documented catastrophic failure modes stemming from oiling system deficiencies, and the transmission cooling system is a known weak point.
M275 Engine Connecting Rod Bearing Failure
Common · high severity
Typical onset: 40,000-80,000 mi
Symptoms: Metallic knocking or rattling from bottom end, especially cold start, Metal shavings visible in oil during changes, Sudden catastrophic loss of oil pressure and engine seizure
Fix: This is the death knell for these engines. Inadequate oiling to rod bearings under high load causes wear, then spin. Requires complete engine-out teardown, crank machining or replacement, new bearings, often new rods and pistons due to collateral damage. 60-80 hours labor minimum for short block rebuild; many shops recommend factory long block due to liability. Preventive bearing replacement at 50k intervals can help but most owners discover this too late.
Estimated cost: $25,000-45,000
Piston Ring Land Failure / Cylinder Scoring
Occasional · high severity
Typical onset: 50,000-100,000 mi
Symptoms: Excessive oil consumption (more than 1 qt per 1,000 mi), Blue smoke on deceleration or startup, Loss of compression in one or more cylinders, Check engine light with misfire codes
Fix: Carbon buildup and heat cause piston ring lands to crack or rings to seize, scoring cylinder walls. Requires complete engine disassembly, cylinder boring/honing, oversize pistons, new rings. Often discovered during bearing failure investigation. 70-90 hours engine-out. Many opt for used or remanufactured engine rather than machine work due to cost and downtime.
Symptoms: Transmission fluid in coolant (strawberry milkshake appearance in expansion tank), Coolant in transmission (delayed engagement, slipping), Overheating transmission or engine, Harsh shifts or limp mode
Fix: Internal leak in transmission oil cooler allows coolant and ATF to mix. Requires new cooler, complete flush of both systems, often new transmission if caught late (clutches toast from coolant). Radiator and all hoses recommended. Engine flush if coolant entered oil via turbo plumbing. 8-12 hours if just cooler; 25-35 hours if transmission replacement needed.
Symptoms: Rattling noise from engine bay at idle or light throttle, Loss of boost pressure / reduced power, Overboost or underboost fault codes, Oily residue around turbo or intercooler connections
Fix: Wastegate actuator arms wear and rattle, eventually seize or fail to regulate boost. Replacement turbos are eye-wateringly expensive from Mercedes. Aftermarket rebuilds available but quality varies. 12-16 hours per side, both recommended if one fails due to age. Oil and coolant lines, gaskets, and intercooler inspection mandatory during job.
Estimated cost: $6,000-12,000 per turbo (OEM), $8,000-18,000 both
ABC Active Body Control Hydraulic Leaks
Common · medium severity
Typical onset: 60,000-100,000 mi
Symptoms: Vehicle sagging at one or more corners after sitting, ABC warning light with 'Visit Workshop' message, Hydraulic fluid puddles under car (green fluid), Harsh ride or loss of self-leveling function
Fix: ABC struts, lines, and pump develop leaks. Struts are most common culprit ($2k-3k each), followed by pressure hoses. Pump failure less common but catastrophic ($4k-6k). Diagnosis requires specialized scan tool. Fluid is expensive ($50/L, system holds 8L). Front struts 4-6 hours each, rears 3-4 hours. ABC delete kits exist but compromise ride quality severely.
Estimated cost: $2,500-4,000 per strut, $6,000-10,000 for pump/accumulator
Airmatic Air Suspension Compressor and Line Failure
Occasional · low severity
Typical onset: 80,000-120,000 mi
Symptoms: Compressor runs constantly or cycles frequently, Vehicle sits low, especially after sitting overnight, Airmatic warning on dash, Hissing sound near suspension components
Fix: Air springs crack, airlines rot, compressor wears out from overwork. Compressor replacement 3-4 hours, air springs 2-3 hours each. If caught early (before compressor burns out from leaking springs), springs alone can be done. Delay leads to compressor replacement too. Aftermarket springs available at half OEM cost with similar longevity.
Estimated cost: $1,200-2,000 (compressor), $800-1,200 per air spring
Owner tips
Change engine oil every 5,000 mi or less with quality 0W-40 synthetic (Mobil 1 FS or equivalent) and OEM filters — this is your only defense against bearing failure
Send oil samples to Blackstone Labs every other change starting at 40k mi to monitor bearing wear metals (iron, copper, lead)
Flush transmission fluid every 40k mi and inspect cooler for internal leaks during every coolant service
Budget $3,000-5,000/year for maintenance and repairs after 60k mi, plus an emergency fund of $25k-30k for engine replacement
Pre-purchase inspection must include borescope cylinder inspection, oil analysis, ABC/Airmatic system pressure test, and transmission cooler inspection
Only buy if you have deep pockets and a masochistic streak — spectacular when running, but the M275 engine is a ticking time bomb that can cost more than the car's value to fix, and it's a question of when, not if.
AI-assisted summary drawn from NHTSA recall data, our labor-times database, and platform knowledge. Not a substitute for a pre-purchase inspection on a specific vehicle.
Fitment notes: OEM size: 12V 12Ah AGM (MB A 000 982 07 08 type) · Location: engine compartment, right/passenger side near the firewall (main starter battery lives in the trunk floor well) · Purpose: voltage support / stabilization for electronics during cranking and load peaks
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Control Modules — 2008 Mercedes-Benz S65 AMG
Every control module on the 2007-2013 Mercedes-Benz S65 AMG — where it lives, replacement time, and what it takes to program a replacement. Modules marked dealer / factory tool won't work after a part swap alone — budget for programming.
⚠️ Critical security component; requires online SCN authorization and key programming; part of security triangle; dealer-only replacement in practice
Night View Assist Control Unit (NVA)2.0 hr R&Rdealer / factory tool +0.5 hr▸ programming details
📍 Dashboard, center behind grille
🔧 Xentry/DAS
⚠️ Infrared camera system; optional equipment; requires calibration and aiming
Active Body Control (ABC)1.8 hr R&Rdealer / factory tool +0.8 hr▸ programming details
📍 Front passenger footwell, behind the carpet/kick panel
🔧 Xentry/DAS
⚠️ Hydraulic active suspension; requires system bleed and calibration after replacement; expensive repairs common · Location owner-verified 2026-07-19 (module is inside the cabin — the engine-bay components are the ABC pump/valve blocks, not the control unit).
Electronic Stability Program / Anti-lock Brake System (ESP/ABS)1.5 hr R&Rdealer / factory tool +0.5 hr▸ programming details
⚠️ Multi-contour seats with massage and ventilation; requires memory position relearn
Bi-Xenon Control Unit (XCU)0.5 hr R&Raftermarket tool +0.2 hr▸ programming details
📍 Each headlight assembly (2 units)
🔧 Xentry/DAS or Autel
⚠️ Active curve lighting; per-headlight module; requires adaptation for leveling
Aftermarket tool coverage varies by software version and vehicle build — treat "aftermarket tool" rows as "usually possible" and verify against your tool maker's coverage list before promising a customer. Spot a wrong location or hour? Tell us — corrections ship fast here.
Size-standard part numbers — verify your connector type before buying. Rear blades are model-specific; check the package's vehicle list.
Fuel economy figures are EPA data via fueleconomy.gov (median across matching trims). Performance figures are compiled estimates for the 2008 Mercedes-Benz S65 AMG 6.0L V12 BiTurbo M275 and can vary by trim.
🔧 Built by master technician Chris Hackleman · Master Technician · 20+ years.