Mercedes Benz GLS Class GLS63 Engine ReplacementCompare Prices & Get Quotes
Get quotes today from trusted UK Mercedes Benz GLS Class GLS63 AMG engine specialists. Compare prices on reconditioned, rebuilt and used engines for the hand-built 4.0-litre twin-turbo V8 - supply & fit available nationwide.
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12-Month Warranty
Nationwide Delivery
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From £7,500 to £13,500
Used from £4,500 · Reconditioned from £7,000 · Common codes: M177.980
From £4,500
Tested, bare/short engine
From £7,000
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 GLS Class GLS63 Replacement Engineto Finding the Best Mercedes Benz GLS Class GLS63 Replacement Engine
Most replacements completed within 3-5 days.
Variant HistoryMercedes Benz GLS Class GLS63 - Engine History & Specs at a Glance
The GLS63 AMG launched with the X166 generation in 2012 as the GL63 AMG, powered by the M157 5.5-litre twin-turbo V8 - a thunderous 557-585hp powerhouse carried over from the ML63. In 2019, the all-new X167 GLS63 replaced it with the M177 4.0-litre twin-turbo V8 featuring hot-vee design and, from 2023, 48V EQ Boost mild-hybrid technology. In 2026, Mercedes-AMG unveiled the comprehensively revised M177 EVO with a new flat-plane crankshaft, delivering 603hp and 627lb-ft of torque.
Variant HistoryMercedes Benz GLS Class GLS63 - Engine History & Specs at a Glance
The GLS63 AMG launched with the X166 generation in 2012 as the GL63 AMG, powered by the M157 5.5-litre twin-turbo V8 - a thunderous 557-585hp powerhouse carried over from the ML63. In 2019, the all-new X167 GLS63 replaced it with the M177 4.0-litre twin-turbo V8 featuring hot-vee design and, from 2023, 48V EQ Boost mild-hybrid technology. In 2026, Mercedes-AMG unveiled the comprehensively revised M177 EVO with a new flat-plane crankshaft, delivering 603hp and 627lb-ft of torque.
Mercedes Benz GLS Class GLS63
Fuel TypePetrol (M157: twin-turbo V8; M177: twin-turbo V8 with 48V MHEV on later models)
Engine Size Range4.0L-5.5L (M157: 5,461cc; M177: 3,982cc)
Power Output Range557-612hp across the variant's historyEngine History Timeline
M157 5.5L twin-turbo V8, 557-585hp (GL63 AMG / GLS63 AMG, X166)
M177.980 4.0L twin-turbo V8, 557-612hp (GLS63 AMG / AMG GLS63, X167)
M177.980 with 48V EQ Boost mild hybrid added
M177 EVO 4.0L twin-turbo V8 with flat-plane crankshaft, 603hp
Key Specs Snapshot
Fuel TypePetrol (M157: twin-turbo V8; M177: twin-turbo V8 with 48V MHEV on later models)Engine Size Range4.0L-5.5L (M157: 5,461cc; M177: 3,982cc)Power Output Range557-612hp across the variant's historyYears Produced2012-presentEvery engine fitted to the Mercedes Benz GLS Class GLS63 is covered below, with UK rebuilt pricing and known failure points - from M157 cylinder scoring to M177 oil separator and rear main seal issues.
Mercedes Benz GLS Class GLS63 Engine Codes - Specifications & Replacement CostMercedes Benz GLS Class GLS63 Engine Codes - Specifications & Replacement Cost
5.5L Twin-Turbo V8 (2012-2018)
Power Output557 hp (410 kW) (GL63 / early GLS63); 585 hp (430 kW) (GLS63 S)Torque700-760 NmYears Fitted2012-2018Displacement5,461ccCylindersV8, 32-valve, twin-turbocharged
Compatible Trim Levels
- GL63 AMG
- GLS63 AMG
- GLS63 AMG 4MATIC (X166)
Find your exact engine code, specs and UK replacement cost guide.
Used
Tested, ready-to-fit engine
£3,500-£5,500
Reconditioned
Addressed known issues, tested
£6,000-£8,500
Rebuilt
Full teardown, upgraded internals
£7,000-£11,000
Common Failure
Cylinder bore scoring - the M157 V8 can suffer from cylinder wall wear, leading to oil consumption and, in severe cases, loss of compression. Timing chain wear and oil leaks are also commonly reported on higher-mileage units. Turbocharger oil feed line leaks and high-pressure fuel pump failures have also been documented.
The GLS63's M177 twin-turbo V8 is one of AMG's most impressive modern engines - a hand-built masterpiece assembled in Affalterbach according to the "One man, one engine" philosophy. However, as these vehicles accumulate mileage, several well-documented issues can drive significant repair costs. The most frequent and expensive problem is oil separator failure, which often leads to rear main seal leaks. Every rebuilt engine supplied through EnginesMarket includes upgraded components addressing the original failure point, plus a minimum 12-month unlimited-mileage warranty.
The Most Expensive M177 Problem
Affected Vehicles
Mercedes GLS63 AMG 4MATIC+, AMG GLS63 4MATIC+ (M177.980, 2019-present)
Typical Failure Mileage
40,000-80,000 miles
Root Cause
The oil-vapour separator (cyclonic separator) is a known weak point on the M177 engine. When the separator becomes blocked, crankcase pressure increases significantly, and the weakest point in the crankcase seal system - the rear main crankshaft oil seal (RMS) - fails. This can start as a whistling noise or rough idle before escalating to a blown rear main seal. Mercedes-Benz mandates that both oil separators be replaced whenever a rear main seal is found leaking to prevent repeat failure.
Why It Happens
The oil-vapour separator (cyclonic separator) is a known weak point on the M177 engine. When the separator becomes blocked, crankcase pressure increases significantly, and the weakest point in the crankcase seal system - the rear main crankshaft oil seal (RMS) - fails. This can start as a whistling noise or rough idle before escalating to a blown rear main seal. Mercedes-Benz mandates that both oil separators be replaced whenever a rear main seal is found leaking to prevent repeat failure.
Dealer (parts + labour)
£250-£450
Specialist (parts + labour)
£180-£320
What it involves
Check crankcase pressure, inspect oil separators, test for vacuum/pressure
Suitability
Confirms whether separator or seal is the root cause
1 - 2 daysDealer (parts + labour)
£1,000-£1,600
Specialist (parts + labour)
£600-£950
What it involves
Replace both oil separators (PCV valves), inspect crankcase ventilation system
Suitability
If caught before seal damage occurs
1 - 2 daysDealer (parts + labour)
£3,500-£5,000
Specialist (parts + labour)
£2,500-£3,800
What it involves
Replace rear main seal, drop transmission, inspect flywheel
Suitability
If seal has failed but no bottom-end damage
1 - 2 daysDealer (parts + labour)
£12,000-£18,000
Specialist (parts + labour)
£7,500-£13,500
What it involves
Supply & fit rebuilt M177 with upgraded oil separators, new rear main seal, full gasket set
Suitability
If oil loss has caused bearing or bottom-end damage
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 |
|---|---|---|---|---|---|
 Diagnosis - Oil separator/PCV check Minor | £250-£450 | £180-£320 | Check crankcase pressure, inspect oil separators, test for vacuum/pressure | Confirms whether separator or seal is the root cause | 1 - 2 days |
 Intermediate - Oil separator replacement Best Value | £1,000-£1,600 | £600-£950 | Replace both oil separators (PCV valves), inspect crankcase ventilation system | If caught before seal damage occurs | 1 - 2 days |
Major - Rear main seal replacement Best Value | £3,500-£5,000 | £2,500-£3,800 | Replace rear main seal, drop transmission, inspect flywheel | If seal has failed but no bottom-end damage | 1 - 2 days |
Full Replacement - Rebuilt M177 engine Best Value | £12,000-£18,000 | £7,500-£13,500 | Supply & fit rebuilt M177 with upgraded oil separators, new rear main seal, full gasket set | If oil loss has caused bearing or bottom-end damage | 1 - 2 days |
Vehicle Value Check
Vehicle Value Check
A typical 2019-present GLS63 AMG 4MATIC+ is worth approximately £45,000-£85,000 depending on mileage and condition. The GLS63 sits firmly in the £15,000+ band - replacement cost is typically small relative to vehicle value, making a full rebuilt engine a justifiable investment for owners of these high-value performance SUVs.
Our Recommendation
Our Recommendation
The oil separator is the root cause of most M177 rear main seal leaks. If you notice oil around the transmission bellhousing, a burning oil smell, or hear a whistling noise from the engine, have the crankcase pressure checked immediately. If caught early, replacing the oil separators alone (£600-£950 at a specialist) prevents the much more expensive rear main seal replacement. If the rear main seal has already failed, replacing both the seal and the oil separators together is the only sensible approach. On a GLS63 worth £45,000-£85,000, the full rebuilt engine route is justifiable if bottom-end damage has occurred.
Don't Let Oil Separator Failure, Rear Main Seal Leaks, or Turbo Issues Write Off Your Mercedes GLS63 AMG
Whether you're facing M177 oil separator failure on your GLS63, rear main seal leaks, or turbocharger issues, 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 - improved oil separators, reinforced rear main seals, and bench-tested turbos - 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 M177 Mercedes GLS63 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 GLS Class GLS63. Every engine supplied through EnginesMarket carries a minimum 12-month unlimited mileage warranty - always confirm exact terms with your chosen supplier."
Mercedes Benz GLS Class GLS63 Engine ReplacementFrequently Asked Questions
Question 1How much does a Mercedes GLS63 AMG engine replacement cost in the UK-
Short summary: A rebuilt M177 V8 engine for the GLS63 costs £7,500-£13,500 supply-only; a rebuilt M157 V8 for earlier models costs £7,000-£11,000 supply-only. Fitting adds £1,500-£2,500 depending on complexity - AMG V8 work requires specialist knowledge.
- GLS63 (M177.980): rebuilt unit £7,500-£13,500; used engine from £4,500
- GL63/GLS63 (M157): rebuilt unit £7,000-£11,000; used engine from £3,500
- M177 oil separator replacement (labour only): £600-£950 at specialist
- M177 rear main seal replacement (labour only): £2,500-£3,800 at specialist
Question 2What are the signs of oil separator failure on a Mercedes GLS63-
Short summary: The most common sign is a burning oil smell or oil dripping from the rear of the engine. A whistling noise or rough idle can also be early indicators. If ignored, oil separator failure leads to rear main seal leaks and potentially bottom-end damage.
- Oil around the transmission bellhousing - classic sign of rear main seal leak
- Burning oil smell from the engine bay
- Whistling or howling sound from the engine at idle
- Rough idle or vibration - can indicate crankcase pressure issues
- If caught early, oil separator replacement costs £600-£950
Question 3Is the Mercedes GLS63 V8 engine (M177) reliable-
Short summary: The M177 is a fundamentally strong hand-built AMG V8 - one of Mercedes' most impressive modern engines. It has a small number of well-documented weak points (oil separator, rear main seal, turbocharger bearings) that are well understood by specialists. With proper maintenance, the M177 routinely exceeds 100,000 miles.
- M177 is a hand-built AMG masterpiece assembled in Affalterbach
- Oil separator and rear main seal issues are the most frequent problems
- Turbocharger bearing degradation due to hot-vee design
- Regular oil changes (every 10,000 miles) are essential - use MB 229.5 spec oil
Question 4How long does a Mercedes GLS63 engine last-
Short summary: Properly maintained M177 V8 engines routinely reach 100,000-150,000 miles before major work, though oil separator and rear main seal issues can occur from 40,000 miles.
- M177 (2019-present): 100,000-150,000 miles with regular servicing
- Oil separator and rear main seal issues from 40,000-80,000 miles
- Service interval is 10,000 miles or 12 months - use Mercedes-spec oil only
- Late oil changes accelerate oil separator failure and turbocharger wear
Question 5Is it worth replacing the engine in my Mercedes GLS63-
Short summary: Yes, if the GLS63 is otherwise in good condition with no rust or major electrical faults. A rebuilt M177 costs £7,500-£13,500 - far less than replacing a £45,000-£85,000 vehicle. The GLS63's strong residual values make engine replacement financially justifiable.
- GLS63 values: £45,000-£85,000 depending on year, mileage and condition
- Rebuilt engine with upgraded components fixes original weak points
- Supply & fit typically £9,000-£16,000 depending on engine code
- New engine includes 12-month unlimited mileage warranty
Question 6What oil does my Mercedes GLS63 AMG need-
Short summary: Mercedes-Benz specifies MB 229.5 high-performance oil - typically 5W-30 or 5W-40 fully synthetic. The M177 V8 requires approximately 9.5 litres.
- M177 (GLS63): MB 229.5 5W-30 or 5W-40 - high-spec synthetic only
- Never use non-approved oil - destroys timing chain tensioners and hydraulic lifters
- Change every 10,000 miles or 12 months - stretched intervals cause oil separator failure
- The 48V system (on later models) requires specialist maintenance
Why Choose UsCompare Mercedes GLS Class GLS63Engine PricesToday
100+ AMG V8 engines supplied through our network
12-Month Warranty on every rebuilt GLS63 engine
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supply & fit available for M157 and M177
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