Mercedes-Benz AMG GT 43 Engine Replacement Compare Prices & Get Quotes

A replacement M139 engine for a GT 43 typically costs between £3,000 and £9,500 depending on condition. Used units start from £3,000-£5,500, reconditioned from £5,500-£7,500, and fully rebuilt from £6,000-£9,500. Labour for supply & fit adds £800-£1,500 for AMG-specialist work. A typical GT 43 is worth £90,000-£120,000, making engine replacement a viable investment for well-maintained cars.

• Used M139: £3,000-£5,500
• Reconditioned M139: £5,500-£7,500
• Rebuilt M139: £6,000-£9,500

The GT 43 uses the M139 engine, which has a timing chain, not a belt. Like other high-performance AMG engines, the timing chain is designed to last the life of the engine with proper maintenance. However, chain stretch can occur on higher-mileage units - a rattling noise on cold start is the classic warning sign.

• M139: timing chain - durable but can stretch
• Regular oil changes are critical for chain longevity

Common signs of engine problems in the GT 43 include: a rattling noise on cold start (timing chain issues), whistling from the engine bay or loss of power (turbocharger leaks), overheating after spirited driving (cooling system strain), blue smoke or frequent oil top-ups (excessive oil consumption), and rough idle or misfire codes (spark plug or fuel system issues).

• Whistling or power loss - turbocharger leaks
• Overheating - cooling system strain
• Blue smoke - oil consumption

It depends on the car's condition and mileage. A GT 43 is typically worth £90,000-£120,000 - a rebuilt M139 engine (£6,000-£9,500) is usually well within the car's value and can be a worthwhile investment if the car is in good condition. For lower-value examples or those with multiple issues, a specialist repair (turbo, cooling system, oil consumption) may be more economical than a full replacement.

• Vehicle worth £90,000-£100,000: rebuilt engine viable for good condition cars
• Vehicle worth £100,000+: rebuilt engine usually justifies cost
• Preventative repairs: often more economical than full replacement

Both the GT 43 and A45 S use the M139 2.0-litre four-cylinder engine with identical power outputs - 416 hp (421 PS) and 500 Nm of torque. The key differences are the drivetrain configuration (rear-wheel drive in the GT 43 vs all-wheel drive in the A45 S) and the vehicle application. The GT 43 also features the electric exhaust gas turbocharger with 48V mild hybrid assistance, which is shared with the A45 S.

• GT 43: 416 hp, 500 Nm, rear-wheel drive
• A45 S: 416 hp, 500 Nm, all-wheel drive
• Same M139 engine architecture, different drivetrain

Power loss in the GT 43 is most commonly caused by turbocharger leaks, which can result in boost lag, whistle, and low power. Other causes include fuel system issues (HPFP failure), spark plug or misfire problems, and timing chain stretch. A diagnostic check with Mercedes STAR/XENTRY or compatible equipment is essential to identify the exact cause.

• Turbocharger leaks - most common cause of power loss
• Fuel system issues - HPFP or injector problems
• Timing chain stretch - rattling + power loss