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Mercedes M273 5.5/4.7L Engine Review

M273 5.5/4.7L Engine

The Mercedes-Benz M273 engine family includes a 5.5-liter and 4.7-liter gasoline V8s based on M272 V6. The M273 series was released in 2005 as a successor for the M113 engine. The new V8 was used in many expensive models of the German manufacturer in the 2000s, such as W211, W221, and X164.

The 5.5L and 4.7L V8s are completely aluminum engines. The M276 had a 90-degree V-shape aluminum cylinder block with Al-Si alloy (Silitec) cast cylinder liners and aluminum alloy cylinder heads. Inside an aluminum crankcase, there is a forged steel crankshaft secured by reinforced bearing caps. The engine is equipped with fracture-split, forged connecting rods and light-weight, low-friction aluminum pistons. The engine block of 4.7L M273 46 KE has 92.9 mm (3.66 in) bores and an 86.0 mm (3.39 in) stroke. The 5.5-liter version (M273 55 KE) has 98.0 mm (3.86 in) bores and a 90.5 mm (3.56 in) stroke. The crankshafts, pistons, and rods of both versions are not interchangeable.

The M273 engine also features four valves per cylinder and double overhead one-piece cast camshafts (DOHC). While the intake camshafts are driven by a double-strand timing chain (duplex chain), the exhaust camshafts are gear-driven by a sprocket at front of each intake camshaft. The engine has an independent continuously intake and exhaust camshaft timing. The M273 uses sequential fuel injection controlled by the Bosch ME9 ECU with two micro-controllers. The cooling system is also managed by ECU - a mechanical thermostat was replaced by a new electronically controlled thermostat for optimum control of engine temperature. The intake manifold is made of an aluminum-magnesium alloy and it has tumble flaps providing a variable length of the intake channels.

In 2010, as a replacement for the M273 engines, Daimler AG introduced the 4.6-liter V8 twin-turbocharged Mercedes-Benz M278 engine.

Engine Specs

Manufacturer
Daimler AG
Production years
2005-2019
Cylinder block material
Aluminum
Cylinder head material
Aluminum
Fuel type
Gasoline
Fuel system
Sequential fuel injection
Configuration
V
Number of cylinders
8
Valves per cylinder
4
Valvetrain layout
DOHC
Bore, mm
92.9 mm (3.66 in) - 4.7L
98.0 mm (3.86 in) - 5.5L
Stroke, mm
86.0 mm (3.39 in) - 4.7L
90.5 mm (3.56 in) - 5.5L
Displacement, cc
4,663 cc (284.6 cu in)
5,461 cc (333.3 cu in)
Type of internal combustion engine
Four-stroke, naturally aspirated
Compression Ratio
10.7:1
Power, hp
335 hp (250 kW)/6,000 - E47
382 hp (285 kW)/6,000 - E55
Torque, lb ft
339 lb-ft (460 Nm)/2,700-5,000 - E47
391 lb-ft (530 Nm)/2,800-4,800 - E55
Engine weight
-
Firing order
1-5-4-2-6-3-7-8
Engine oil weight
MB 229.5, SAE 0W-40
Engine oil capacity, liter
8.5l (9.0 qt)
Oil change interval, mile
9,000 (15,000 km) / 12 months
Applications
E500/E550, CL500/CL550, CLS500/CLS550, GL500/GL550, ML450/ML500/ML550, S450/S500/S550, CLK500/CLK550, GL450, G500, R500

Mercedes M273 Engine Problems and Reliability

Unfortunately, the M273 engines have earned a reputation as one of the most problematic Mercedes V8 engines. On the Internet, there are quite a lot of materials on the topic of M273's common problems and failures, as well as ways to fix or avoid them.

A weak place is engine timing. Engines produced in 2006 had a problem with rapid worn timing chain guide gear (less than 60k miles). This failure could cause a wrong positioning of the camshafts. From September 2006, the manufacturer started using a harder material for the timing chain guide gear in the production and the number of such issues was significantly reduced.

A cam plug oil leak is another widespread problem of this engine family. This is typical for engines manufactured before June 2008. Oil leakage was on the backside of the cylinder heads from the round expansion plugs made of plastic material. Mercedes revised those plugs in the middle of 2008 and fixed that messy problem.

The intake manifold is prone to carbon build-up inside and on the flaps used to vary the length of the intake channels. Dirty flaps could be stuck or create high loads on the plastic VIM actuator cam. In both cases, that will lead to actuator cam breakage. Incorrect operation of the variable intake manifold features the following symptoms: rough idle and a loss of power with check engine light illumination.

Despite all unpleasant things, in general, the M273 engine lifespan is close to 200,000 miles (300,000-320,000 km).

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