The older Mercedes diesels (think from the 70s, 80s, and 90s) were extremely durable vehicles and known to run for a million miles with overall minimal maintenance needs. You would hope for the same performance out of the modern Bluetec diesels, but unfortunately this is not the case. The older diesels traded reliability for being extremely dirty and pollutant-producing engines. The modern Bluetec systems are laden with computers, gadgets, and required additives that do produce a cleaning burning engine, but with significantly more components to break (and commonly do). Cars additionally became much more electronic controlled after this era and created a slew of other reliability issues. At Fremont Auto, we do not advise you to buy a Mercedes Bluetec. But if you do or if you already own one, we do have the experience to service the vehicle for you.
We recently had a 2010 Mercedes ML 350 Bluetec in the shop for a multitude of issues relating to both the Bluetec system and others. One of the main issues was a melted fuse box due to a failed air compressor system for the air ride suspension. It’s unclear what exactly caused the issue – whether the fuse itself overheated due to being faulty, if the air compressor pump ran constantly due to a leak, etc – but the end result was an electrical circuit overheating and melting the entire fuse box in the engine bay. This is a costly repair that required the entire fuse box assembly (which houses fuses for other systems too) to be replaced, along with replacing the suspension’s air compressor itself.
On modern luxury cars like this, though, a part repair or replacement isn’t as simple as just swapping out the failed component. Often these luxury models require that you program the new part into the car’s computer system, otherwise it will not operate (despite the new part being good). After repairing the Mercedes’ air suspension we had to leave the car on a battery charger while our shop’s computer updated all the car’s computer firmware so that the new air suspension would be recognized by the onboard computer. This type of programming is, of course, an added repair expense that you otherwise would not incur on less sophisticated and more reliable makes and models.
Word of Caution
To reiterate, at Fremont Auto we do not recommend that you buy any Mercedes Bluetec products and to take caution buying newer Mercedes products in general. The ML 350 we had in the shop faced costly air suspension repairs before we even tackled this model’s other common issues related to catalytic converters and EGR issues. If you’re in the market for one of these vehicles, please find a suitable alternative or at least let us look the vehicle over for you before purchasing.