Mercedes Benz SL Class SL55/SL63 AMG Engine ReplacementCompare Prices & Get Quotes
Get quotes today from trusted UK Mercedes Benz SL Class SL55 AMG and SL63 AMG engine specialists. Compare prices on reconditioned, rebuilt and used engines for the hand-built supercharged V8 and naturally aspirated V8 - supply & fit available nationwide.
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From £4,500 to £10,000
Used from £2,500 · Reconditioned from £4,500 · Common codes: M113.991, M156.981, M156.982
From £2,500
Tested, bare/short engine
From £4,500
Rod bearings addressed, tested
From quote
Upgraded bearings, full teardown, revised valvetrain
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3 Simple Steps3 Simple Stepsto Finding the Best Mercedes Benz SL Class SL55/SL63 AMG Replacement Engineto Finding the Best Mercedes Benz SL Class SL55/SL63 AMG Replacement Engine
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Variant HistoryMercedes Benz SL Class SL55/SL63 AMG - Engine History & Specs at a Glance
The SL55 AMG and SL63 AMG represent two distinct eras of AMG engineering excellence. The SL55 AMG launched in 2003 with the M113K 5.4-litre supercharged V8 - a hand-built engine producing 493hp and 516 lb-ft of torque. In 2008, the SL63 AMG replaced it with the M156 6.2-litre naturally aspirated V8, producing 518hp and 465 lb-ft of torque. The M113K delivered relentless, supercharged torque that defined the early 2000s AMG experience, while the M156 brought high-revving naturally aspirated character and an iconic soundtrack. Both engines were hand-built in Affalterbach, representing the pinnacle of AMG V8 engineering.
Variant HistoryMercedes Benz SL Class SL55/SL63 AMG - Engine History & Specs at a Glance
The SL55 AMG and SL63 AMG represent two distinct eras of AMG engineering excellence. The SL55 AMG launched in 2003 with the M113K 5.4-litre supercharged V8 - a hand-built engine producing 493hp and 516 lb-ft of torque. In 2008, the SL63 AMG replaced it with the M156 6.2-litre naturally aspirated V8, producing 518hp and 465 lb-ft of torque. The M113K delivered relentless, supercharged torque that defined the early 2000s AMG experience, while the M156 brought high-revving naturally aspirated character and an iconic soundtrack. Both engines were hand-built in Affalterbach, representing the pinnacle of AMG V8 engineering.
Mercedes Benz SL Class SL55/SL63 AMG
Fuel TypePetrol (M113K: supercharged V8; M156: naturally aspirated V8)
Engine Size Range5.4L-6.2L (M113K: 5,439cc; M156: 6,208cc)
Power Output Range493-518hp across the variant's historyEngine History Timeline
M113K 5.4L supercharged V8, 493hp @ 6,100rpm, 700Nm torque (SL55 AMG, R230 launch)
2008 - M113K continues with P030 Performance Package available from 2004
M113K 5.4L supercharged V8, 510hp @ 6,100rpm (facelift SL55 AMG)
M156.981 6.2L naturally aspirated V8, 518hp @ 6,800rpm, 630Nm torque (SL63 AMG, replaces SL55)
2011 - M156.981 continues as the SL63 AMG engine through end of R230 production
Key Specs Snapshot
Fuel TypePetrol (M113K: supercharged V8; M156: naturally aspirated V8)Engine Size Range5.4L-6.2L (M113K: 5,439cc; M156: 6,208cc)Power Output Range493-518hp across the variant's historyYears Produced2003-2011Every engine fitted to the Mercedes Benz SL Class SL55 AMG and SL63 AMG is covered below, with UK rebuilt pricing and known failure points - from M113K supercharger coupler wear to M156 head bolt corrosion.
Mercedes Benz SL Class SL55/SL63 AMG Engine Codes - Specifications & Replacement CostMercedes Benz SL Class SL55/SL63 AMG Engine Codes - Specifications & Replacement Cost
5.4L Supercharged V8 (2003-2008)
Power Output493 hp (368 kW) @ 6,100 rpm (early); 510 hp (380 kW) @ 6,100 rpm (facelift with Performance Package)Torque700 Nm (516 lb-ft) @ 2,600-4,000 rpmYears Fitted2003-2008Displacement5,439 cc (5.4L)CylindersV8, 90° V-angle, SOHC, 24-valve (3 valves per cylinder)Engine CodeM 113.991 (M113K Kompressor)
Compatible Trim Levels
- SL55 AMG
- SL55 AMG Kompressor
- SL55 AMG P030 Performance Package
- SL55 AMG Final Edition
Find your exact engine code, specs and UK replacement cost guide.
Used
Tested, ready-to-fit engine
£2,500-£4,500
Reconditioned
Addressed known issues, tested
£4,500-£6,500
Rebuilt
Full teardown, upgraded internals
£5,500-£8,500
Common Failure
Supercharger coupler and bearing wear - the M113K's supercharger relies on a clutch and bearings to function properly. Over time, these components can wear out, leading to unusual noises, reduced power delivery, and even supercharger failure. Oil leaks from valve cover gaskets are also common. Typical failure mileage: 60,000-90,000 miles.
The SL55's M113K supercharged V8 and the SL63's M156 naturally aspirated V8 are among AMG's most celebrated engines - hand-built masterpieces from Affalterbach. However, both have well-documented weaknesses that can lead to significant repair costs. The M113K suffers from supercharger coupler and bearing wear, while the M156 is notorious for head bolt corrosion. Every rebuilt engine supplied through EnginesMarket includes upgraded components addressing these original failure points, plus a minimum 12-month unlimited-mileage warranty.
The SL55 AMG's Signature Weakness
Affected Vehicles
Mercedes SL55 AMG (M113K, 2003-2008)
Typical Failure Mileage
60,000-90,000 miles
Root Cause
The M113K's supercharger relies on a clutch and bearings to function properly. Over time, these components can wear out, leading to unusual noises, reduced power delivery, and even supercharger failure. The supercharger rear bearings are reportedly unserviceable according to some sources. Merc sees the supercharger as a single replacement unit and offers nothing separately.
Why It Happens
The M113K's supercharger relies on a clutch and bearings to function properly. Over time, these components can wear out, leading to unusual noises, reduced power delivery, and even supercharger failure. The supercharger rear bearings are reportedly unserviceable according to some sources. Merc sees the supercharger as a single replacement unit and offers nothing separately.
Dealer (parts + labour)
£200-£400
Specialist (parts + labour)
£150-£300
What it involves
Supercharger bearing and coupler inspection, belt and pulley check
Suitability
First step - confirms whether rebuild or replacement is needed
1 - 2 daysDealer (parts + labour)
£2,500-£4,000
Specialist (parts + labour)
£1,600-£2,500
What it involves
Replace supercharger coupler, bearings, seals, snout gasket
Suitability
If bearings are serviceable or coupler has failed
1 - 2 daysDealer (parts + labour)
£4,000-£6,500
Specialist (parts + labour)
£2,800-£4,500
What it involves
Replace complete supercharger unit, drive belt, tensioner
Suitability
If bearings have failed catastrophically
1 - 2 daysDealer (parts + labour)
£9,000-£12,000
Specialist (parts + labour)
£5,500-£8,500
What it involves
Complete engine swap with rebuilt supercharger and upgraded components, 12-month warranty
Suitability
If supercharger failure has sent debris through engine
1 - 2 daysAll prices are indicative UK market ranges based on current UK specialist supplier data.| Repair Tier | Dealer (Parts + Labour) | Specialist (Parts + Labour) | What It Involves | Suitability | Estimated Time |
|---|---|---|---|---|---|
 Diagnostics - Supercharger inspection Minor | £200-£400 | £150-£300 | Supercharger bearing and coupler inspection, belt and pulley check | First step - confirms whether rebuild or replacement is needed | 1 - 2 days |
 Intermediate - Supercharger rebuild Best Value | £2,500-£4,000 | £1,600-£2,500 | Replace supercharger coupler, bearings, seals, snout gasket | If bearings are serviceable or coupler has failed | 1 - 2 days |
Major - Supercharger replacement Best Value | £4,000-£6,500 | £2,800-£4,500 | Replace complete supercharger unit, drive belt, tensioner | If bearings have failed catastrophically | 1 - 2 days |
Full Replacement - Rebuilt M113K engine Best Value | £9,000-£12,000 | £5,500-£8,500 | Complete engine swap with rebuilt supercharger and upgraded components, 12-month warranty | If supercharger failure has sent debris through engine | 1 - 2 days |
Vehicle Value Check
Vehicle Value Check
A typical 2003-2008 SL55 AMG is worth approximately £10,000-£25,000 depending on mileage and condition. These performance roadsters retain strong values for well-maintained examples, making engine replacement a justifiable investment.
Our Recommendation
Our Recommendation
M113K supercharger wear is progressive. If you hear unusual noises from the supercharger or notice reduced power, have it inspected immediately. Specialist supercharger rebuild at £1,600-£2,500 is significantly cheaper than dealer rates. If the supercharger has failed catastrophically, a full rebuilt M113K engine with a new supercharger is the only safe option.
Don't Let Supercharger Wear, Head Bolt Corrosion, or Oil Leaks Write Off Your Mercedes SL55 or SL63 AMG
Whether you're facing M113K supercharger coupler wear on your SL55 AMG or M156 head bolt corrosion on your SL63 AMG, EnginesMarket makes it simple to compare quotes from trusted UK Mercedes AMG specialists. Every rebuilt engine in our network carries upgraded components addressing the original design weakness - rebuilt superchargers with new bearings, ARP head studs, and fresh gaskets and seals - plus a minimum 12-month unlimited mileage warranty with nationwide delivery and supply & fit options. Don't pay main dealer premiums. Compare prices from independent AMG specialists who know these hand-built V8 engines inside out.
Compare rebuilt M113K Mercedes SL55 AMG engine prices
12-Month Minimum
UK Specialists Vetted
Best Price GuidanceImportant Information
Important Information
"All prices are indicative UK market ranges based on historical quote data and repair requests from our network of engine specialists. Dealer pricing is estimated based on published main dealer labour rates and genuine OEM parts pricing. Specialist pricing reflects actual quote data from EnginesMarket's UK network. Actual costs vary depending on damage severity, vehicle condition, variant, and workshop location within the UK. Use our free comparison tool to get tailored quotes for your specific Mercedes SL Class SL55 or SL63 AMG. Every engine supplied through EnginesMarket carries a minimum 12-month unlimited mileage warranty - always confirm exact terms with your chosen supplier."
Mercedes Benz SL Class SL55/SL63 AMG Engine ReplacementFrequently Asked Questions
Question 1How much does a Mercedes SL55 or SL63 AMG engine replacement cost in the UK-
Short summary: A rebuilt M113K engine for the SL55 AMG costs £5,500-£8,500 supply-only; a rebuilt M156 engine for the SL63 AMG costs £6,500-£10,000 supply-only. Fitting adds £1,500-£2,500 depending on complexity - AMG V8 work requires specialist knowledge.
- SL55 AMG (M113K): rebuilt unit £5,500-£8,500; used engine from £2,500
- SL63 AMG (M156): rebuilt unit £6,500-£10,000; used engine from £3,000
- M113K supercharger rebuild: £1,600-£2,500 at specialist
- M156 head bolt replacement: £2,500-£4,000 at specialist
Question 2What are the signs of supercharger failure on a Mercedes SL55 AMG-
Short summary: Unusual noises from the supercharger, reduced power delivery, or a persistent squeak are the classic warning signs on the M113K engine. The supercharger clutch and bearings wear out over time, leading to potential supercharger failure if ignored.
- Rattling or clattering noise from the supercharger area
- Dreaded continual squeak - often indicates rear bearing wear
- Reduced power or boost pressure
- If caught early, supercharger rebuild costs £1,600-£2,500 at specialist
Question 3What are the signs of head bolt failure on a Mercedes SL63 AMG-
Short summary: "Top up coolant" warnings, unexplained coolant loss, or misfires are the classic warning signs on the M156 engine. The original head bolts had a defect in the anti-corrosive coating and a weaker hollow torx bolt head design.
- "Top up coolant" warning on the dash
- Unexplained coolant loss without visible external leaks
- Engine misfire or rough running
- Check engine light with cylinder-specific fault codes
- Engine numbers below 60,060,658 are affected
Question 4Which AMG engine is more reliable - the M113K or the M156-
Short summary: The M113K is widely regarded as one of the most reliable AMG engines ever built, with a reputation for bulletproof V8 engineering. The M156 is a high-revving masterpiece but has known head bolt issues. With the head bolts addressed, the M156 is also a fundamentally strong engine.
- M113K is considered bulletproof - supercharger wear is the main concern
- M156 head bolt corrosion affects 2007-2011 production engines
- M156 engine numbers below 60,060,658 require preventative attention
- Both engines exceed 100,000 miles with proper maintenance
Question 5How long do Mercedes SL55 and SL63 AMG engines last-
Short summary: Properly maintained M113K and M156 engines routinely reach 150,000-200,000 miles before major work. Supercharger wear on the M113K typically appears between 60,000-90,000 miles, while M156 head bolt issues can occur from 20,000 miles.
- M113K (SL55 AMG): 150,000-200,000 miles with regular servicing
- M156 (SL63 AMG): 150,000-200,000 miles - head bolt inspection from day one
- Supercharger inspection recommended from 60,000 miles on M113K
- Service interval is 10,000 miles or 12 months - use Mercedes-spec MB 229.5 oil
Question 6Is it worth replacing the engine in my Mercedes SL55 or SL63 AMG-
Short summary: Yes, if the SL is otherwise in good condition with no rust or major transmission faults. A rebuilt M113K costs £5,500-£8,500 - far less than replacing a £10,000-£25,000 vehicle. The SL63 AMG's higher value (£15,000-£35,000) makes replacement even more financially justifiable.
- SL55 AMG values: £10,000-£25,000 depending on year, mileage and condition
- SL63 AMG values: £15,000-£35,000 - AMG values remain strong
- Rebuilt engine with upgraded components fixes original weak points
- Supply & fit typically £7,000-£12,500 depending on engine code
- New engine includes 12-month unlimited mileage warranty
Why Choose UsCompare Mercedes SL Class SL55/SL63 AMGEngine PricesToday
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supply & fit available for M113K and M156
Comparing quotes for your Mercedes SL55 or SL63 AMG is completely free, with no obligation and no pressure. Enter your registration above to get tailored quotes from UK Mercedes AMG specialists who understand the M113K supercharged V8 and the M156 naturally aspirated V8 inside out. Whether you need a used engine, a reconditioned unit, or a full rebuilt engine with upgraded supercharger components, ARP head studs, and fresh gaskets, we'll connect you with the right specialist for your exact SL - with a minimum 12-month warranty on every engine supplied.
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