The Mercedes Om617 engine is a legendary diesel power plant known for its robustness and longevity. For those considering a classic Mercedes diesel, understanding the OM617 is crucial. Let’s delve into what makes this engine special, especially when compared to its contemporaries and later iterations.
One common misconception about 5-cylinder engines is vibration. However, the OM617 defies this. For a five-cylinder diesel, the Mercedes OM617 is remarkably smooth. Potential buyers of a vintage 300D or 300SD needn’t worry about excessive vibration detracting from the driving experience. Many owners, including those of ’85 300D-T models, have been thoroughly impressed with the engine’s refined operation.
Moving on to comparisons with later engines, the OM603, while more modern, is sometimes unfairly criticized for head problems. It’s important to note that any engine with an alloy head can be susceptible to issues if overheated. Often, reported OM603 head problems stemmed from cooling system failures exacerbated by drivers attempting to continue driving instead of immediately stopping, leading to head cracks. Early OM603 heads (#14) did have a slightly higher risk due to less space between oil and water passages. If opting for an OM603-equipped Mercedes, seeking models with a #17 or later head is advisable. However, many owners, including those with the earlier #14 heads, have experienced no issues.
In terms of routine maintenance, a key difference between the Mercedes OM617 and OM603 engines lies in valve adjustments. The OM617 engine requires regular valve adjustments, a standard procedure for older engines. In contrast, the OM603 features hydraulic lifters, which are self-adjusting, reducing this particular maintenance task.
When considering models, the 1987 300D Turbo with the OM603 engine (W124 chassis) represents a significantly more modern car overall compared to the 1982-85 300D-T with the OM617 engine (W123 chassis). The W124 generation boasts advancements such as a driver airbag, ABS, and a more sophisticated suspension system, resulting in a quieter and smoother ride. Conversely, the W123 embodies the “classic” Mercedes-Benz feel, often considered the last of its kind in terms of pure, unadulterated Mercedes engineering. Some might even describe the W123’s driving experience as more agricultural – “like a tractor,” as some owners humorously note, highlighting its robust and direct nature.
Ultimately, regardless of whether you choose a Mercedes with an OM617 or a later engine, the golden rule is to buy the best example your budget allows. A cheap Mercedes-Benz can quickly become a costly burden, leading to regret. While the more modern W124 offers more features and refinement, it also inherently has more components that could potentially fail. If you are comfortable with DIY maintenance, this might be less of a concern. However, entrusting a Mercedes to professional mechanics can be expensive. The key takeaway is that any Mercedes, regardless of engine, demands diligent maintenance. Therefore, prioritize finding a car with comprehensive service records to ensure a more predictable and enjoyable ownership experience.
