The summary of ‘The Mercedes Benz OM651: Is it a good engine?’

The video focuses on the Mercedes-Benz OM 651 engine, discussing its reliability, issues with the timing chain and tensioner, vacuum pump problems, emissions systems, and various components like the fuel pump. The complexity of the engine layout, maintenance needs, and potential challenges in accessing and replacing certain components are highlighted. Mentioned components include the camshafts, water pump, vacuum pump, electric power steering system, fuel pump, diesel particulate filters (DPFs), emission system components, and diesel exhaust systems with SCR catalysts and oxygen sensors. The video emphasizes the advantages of electric steering racks over hydraulic systems and notes that maintenance requirements and potential issues vary across different models. The reliability of emission systems and diesel engines, particularly the DPFs and AdBlue/DEF systems, is discussed, with a focus on repairability and component replacement. The video hints at upcoming content on transmission fluid flush and servicing the transfer case.

00:00:00

In this segment of the video, the focus is on the Mercedes-Benz OM 651 engine. The engine was used in various vehicles in Europe and the United States, including E-Classes, S-Classes, C-Classes, GLS, GLK, and GLE. The video delves deep into the engine’s reliability, covering issues such as the timing chain, tensioner problems, potential vacuum pump issues, and emissions systems problems. While there are concerns about the timing chain, the main issue is usually the tensioner. Unlike previous engines, the OM 651’s entire Timing System is at the back, which complicates other systems like the vacuum pump and fuel pump. There is also controversy about the chain, as earlier engines had double row timing chains, while the OM 651 uses a single row timing chain.

00:03:00

In this segment of the video, the speaker discusses the timing chain system in a specific engine, highlighting that only the camshafts are driven by the timing chain, with other components being gear-driven off the crankshaft. Maintenance tips, such as replacing the tensioner, are emphasized. The location of the timing chain at the back of the engine is detailed, leading to challenges in accessing and replacing the fuel pump, making it a more complex task compared to older diesel engines. The injector types and potential interchangeability with other models are also touched upon, with cost estimates provided.

00:06:00

In this segment of the video, the speaker discusses the layout of the engine components, focusing on the vacuum pump’s positioning at the back of the engine and the water pump’s location at the front. They mention that most USC cars have vacuum-controlled water pumps for efficient heating of the engine. The speaker notes the potential issues with the water pump’s main shaft seal leaking coolant and the risk of coolant entering the vacuum system if the vacuum pump fails. The video also highlights the unique feature of this vehicle having an electric power steering system instead of a traditional power steering pump, emphasizing the advantages of reduced fluid leaks and complexity.

00:09:00

In this segment of the video, the presenter discusses the benefits of electric steering racks over hydraulic systems due to being self-contained and less complex without the need for a power steering pump. They mention the maintenance requirements for the 4MATIC system in the front transfer case and the potential issues with shaft seals leaking, particularly in the GLK model. The presenter also highlights the location of the fuel pump and the complexity of the emission system and exhaust components, noting the presence of two diesel particulate filters (DPFs) in the vehicle.

00:12:00

In this segment of the video, the speaker explains the various components of a modern diesel exhaust system, including pressure sensors, diesel exhaust fluid injectors, SCR catalysts, and oxygen sensors. The speaker notes that while these emission systems can be complex and costly to repair, newer diesel models have more modularized exhaust systems, allowing for easier component replacement. The reliability of these systems is still somewhat unknown, with the speaker pointing out that components within the emission system are likely to require replacement over time, but not all at once. Individual parts like oxygen sensors or the SCR catalyst may need maintenance, but the entire system usually does not need complete replacement simultaneously.

00:15:00

In this part of the video, the speaker discusses the issues related to diesel particulate filters (DPFs) in vehicles. They mention that DPFs themselves usually do not go bad, and if you encounter a code indicating a clogged DPF, it can often be resolved by cleaning it out. The speaker expresses interest in the emission system, particularly the AdBlue/DEF system, and the reliability of these newer diesel engines. They suggest that if any issues arise, they will make a video about it. The video ends with a preview of upcoming content on transmission fluid flush and servicing the transfer case.