The company produced the 4.0-liter Mercedes OM629 diesel engine between 2005 and 2010, but it was only used in the company’s biggest and priciest models, like the W211, W221, and X164. There was only one DE 40 LA motor available, but it had two distinct indexes: 420 CDI and 450 CDI.
OM628 and OM629 are members of the diesel V8 family.
Similar to the OM 628, the OM 629 engine has a displacement of 3996 cc. The aluminum cylinder block has cast iron liners. For space reasons, the camber is 75° and the cylinder spacing is 97 mm. The engine has two camshafts per cylinder head (four valves per cylinder), a liquid intercooler, a balancing shaft in the cylinder block’s camber, a cooled exhaust gas recirculation system, and variable geometry turbochargers for each cylinder bank.
Specifications
| Production years | 2005-2010 |
| Displacement, cc | 3996 |
| Fuel system | Common Rail |
| Power output, hp | 306 – 320 |
| Torque output, Nm | 700 – 730 |
| Cylinder block | aluminum V8 |
| Block head | aluminum 32v |
| Cylinder bore, mm | 86 |
| Piston stroke, mm | 86 |
| Compression ratio | 17.0 |
| Features | intercooler |
| Hydraulic lifters | yes |
| Timing drive | double row chain |
| Phase regulator | no |
| Turbocharging | two GTB1752VK |
| Recommended engine oil | 5W-30 |
| Engine oil capacity, liter | 10.5 |
| Fuel type | diesel |
| Euro standards | EURO 4 |
| Fuel consumption, L/100 km (for Mercedes GL 420 CDI 2007) — city — highway — combined |
15.6 9.2 11.6 |
| Engine lifespan, km | ~280 000 |
| Weight, kg | 280 |
The engine was installed on:
- Mercedes E-Class W211 in 2006 – 2009;
- Mercedes GL-Class X164 in 2006 – 2010;
- Mercedes ML-Class W164 in 2007 – 2010;
- Mercedes S-Class W221 in 2005 – 2010.
Disadvantages of the OM629 engine
Although this diesel engine is now more dependable than its predecessor, it still causes a lot of problems.
Injection pump failures and pouring fuel injectors are the primary issues.
Particularly for the EGR system, this unit cokes very quickly.
Additionally, the engine is terrified of overheating, which can lead to cracks and scuffs.
The timing chain stretches and the turbine frequently fails after 200,000 kilometers.
Distinctions between the OM629 and its predecessor engines:
- enhanced boost pressure, which increases power and torque;
- GTB turbochargers;
- a 17:1 compression ratio;
- and a newly installed DPF.
Along with the aforementioned modifications, the engine now has new turbines, 1600 bar injection systems, and piezoelectric injectors. The amount of air pumped into the cylinders could be increased by 15% by lowering the pressure loss in the intake tract. Additionally, it was possible to raise the density at the engine intake by 25% and lower the temperature of the inflated air to 120° C by using intercoolers.
Explanation of OM629 marking
| OM | Heavy Fuel Oil (Diesel) engine |
| 629 | Engine type: 8-cylinder |