OM651 Engine: Bulletproof Workhorse or Total Money Pit? Is it worth buying?
Hey everyone,
I’m currently looking at buying a Mercedes with the OM651 engine (the 2.1L diesel), but I’m seeing incredibly polarizing opinions online. Some people say it'll outlive the chassis, while others say it’s an absolute engineering nightmare.
I want some direct, unfiltered opinions from owners or mechanics. Here is what I’ve gathered so far in terms of Pros and Cons. Tell me if I’m missing something:
Pros:
The Block is Rock Solid: I’ve seen Taxis (E-Class) and Sprinter vans with 500k+ km on the original block. It seems to take a beating well.
Great Torque: For a 4-cylinder, the low-end pull (especially in the twin-turbo 220/250 CDI variants) is pretty damn impressive.
Fuel Efficiency: Excellent MPG considering the heavy cars/vans it moves around.
Cons:
The Timing Chain Nightmare: Putting the timing chain at the back of the engine?! I know the chain itself is cheap, but the labor of pulling the engine or dropping the transmission just to replace it sounds like a financial disaster.
The Delphi Piezo Injector Fiasco: I know the early ones (2008-2012ish) were prone to sudden death and there was a massive recall to swap them to solenoids.
Cooling System Leaks: Water pump issues and brittle plastic coolant flanges that crack and leak over time.
Intake/EGR Carbon: Swirl flaps getting stuck or breaking due to heavy carbon buildup in the intake manifold.
My Question:
If I find one with a documented service history—specifically where the injectors were swapped and the timing chain was recently done is it a safe buy? Or is it still a ticking time bomb that will drain my wallet in labor costs at the mechanic?
Give it to me straight. Appreciate the help!