The first Mercedes common rail diesel was introduced in late 1997. It was a 2.1 CDI engine marked OM 611 with power from 82 to 204 hp. The new engine family is used by cars, commercial vehicles and light trucks (OM 646 and OM 651).
Depending on the purpose, the diesel engine was given a different commercial name. For example, 180 CDI, 200 CDI, 220 and 250 CDI CDI. There are also modifications of BlueTEC and BlueEFFICIENCY.
Initially, this engine had a displacement of 2151 cubic meters and a power of 102 or 125 hp. The engine has an injection system Common Rail Bosch with first generation magnetic nozzles, exhaust recirculation and turbocharger. Chain as a drive reduces maintenance costs.
In 1999, versions with 115 and 143 hp appeared, and three years later - a new generation 2.1 CDI with the designation OM 646 and power of 122 and 150 hp. Other modifications were later introduced. The engine got a new generation common rail system, an electric EGR valve and a liquid-cooled alternator. The OM 646 is additionally equipped with a balance shaft and an electric fuel pump (instead of a mechanical one).
The 2.1 CDI engine marked OM 651 debuted in 2008. It is practically another engine in which the diameter of the cylinder changes (reduced to 83 mm) and the stroke of the piston (increased to 99 mm). The displacement of the new version of the engine is 2143 cm3. The compression ratio is reduced to 16.2: 1. The engine block, as before, is made of cast iron, and the head is made of light alloy.
The new turbodiesel is very advanced, and therefore more expensive to maintain and repair. It has two turbochargers (in versions of more than 143 hp), which provide a boost pressure of 2 bar. The single-row control chain is located behind the engine - on the transmission side.
The more powerful version of the engine uses piezo injectors Delphi. Injection pressure up to 2000 bar. For comparison, the injection pressure OM 611 - 1350 bar. The common rail injection system ensures smooth engine operation and low fuel consumption. Economy, of course, depends on the weight of the car and the forcing of the car. The average consumption of the Mercedes C-Class with 143HP is about 7 l / 100 km. Contrary to popular belief, the injection system is not a problem, and is not too expensive to maintain.
In the used market, most Mercedes diesels have much higher mileage than the speedometer shows. Hence the problems faced by other and subsequent owners. The turbine and floating flywheel rarely manage to cover 150000 km.
Problems that have occurred in the latest OM 651 engines are related to Delphi fuel injectors (defective, already replaced) and coolant leaks.
The most common 2.1 CDI engine failures
Most often they are the owners Mercedesa with high mileage and a 2.1 CDI engine you have trouble starting in the morning and dropping power. In both cases, there are several reasons. Problems with starting the system, usually refers to the pressure drop in the injection system due to a malfunction of the pump, nozzles or high pressure valve. The power drop can be caused by a malfunction of the valve in the intake manifold.
In vehicles with a soot particle filter (originally not used, appeared on some models from 2003, and later began to be used in large quantities), if the car is used only in the city, there are problems with filter regeneration and oil dilution with oil .
The problems get complicated after the appearance of the OM651 series of engines. Nozzles break down about 50.000 km. Some sources report that the shortage affected about 300 cars.
Alternator pulley
Alternator pulley
The pulley alternator in + can often fail. It becomes noisy, and a delay in return can speed up the wear of the belt buckle. Solving the problem is not complicated and not too expensive.
Electromagnetic valve
Electromagnetic valve
Solenoid valves are used to control the turbocharger and EGR valve (old engine 2.1). When not working, a power drop occurs.
Nozzles
Symptoms: starting problems, excessively high fuel consumption and unequal operation. Nozzles can be repaired.
Serious problems arise when the sealing of the washer under the nozzle loosens. Removing the injector is a difficult task.
Thermostat
Symptoms: too slow engine warm-up. Thermostat to open already at temperatures of 45 degrees. Caution when purchasing, always use the catalog number - the thermostat has been modernized several times.
OM 651 engine problems
- Injectors. Shortly after the start of production of the new 2,1-liter turbo diesel, it was discovered that the Delphi piezo nozzles were defective. Replacement needed.
- Coolant leaks. Uncontrolled leakage of antifreeze can cause the engine to overheat. The culprit is the coolant pump. The faulty pump must be replaced.
- Valves in the intake manifold. The flaps wear out and break. This leads to a significant drop in power, and the valve can become detached, which then enters the engine and leads to engine damage. Due to the lack of special elements, the whole branch must be changed.
Hi there, I am Mladen and I am an auto enthusiast. I started this blog years ago to help like minded people share information about latest cars, car servicing ideas, used car info, exotic cars, and auto technology. You will find helpful articles and videos on a wide variety of cars - Audi, Mercedes, Toyota, Porsche, Volvo, BMW and much more. Ping us if you have anything cool to share on latest cars or on how to make older cars more efficient, or just want to say hi!
Hi there, I'm Mladen and I'm an auto enthusiast. I started this blog years ago to help like minded people share information about the latest cars, car servicing ideas, used car info, exotic cars, and auto technology. You will find helpful articles and videos on a wide variety of cars - Audi, Mercedes, Toyota, Porsche, Volvo, BMW and much more. Ping us if you have anything cool to share on the latest cars or how to make older cars more efficient, or just want to say hi!
Greeting. I am interested in your opinion about the w211, 220cdi 170hp, means redesign, with a 646 engine, as they turned out, because I plan to buy it, and what to pay attention to when buying
Thank you very much
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Greeting. I am interested in your opinion about the w211, 220cdi 170hp, means redesign, with a 646 engine, as they turned out, because I plan to buy it, and what to pay attention to when buying
Thank you very much