Mercedes decided that they wanted to create a compact executive car to replace their older 190 model, and so, in 1987, their engineers began to work fervently on crafting the C Class, AKA the W202. The first generation C Class ran from 1993 to 2000, and while it did share a similar design platform to the popular 190, the C Class featured a far smoother design with rounder edges than its predecessor. Unfortunately, some of the earlier C Class models contained faulty batteries that occasionally exploded, causing Mercedes to issue a recall.
If you start your car and then hear what sounds like a shotgun blast underneath your hood, chances are the battery just exploded. There are no vibrant outward signs that will tell you if this is about to happen, just a few subtle things (like knowledge of electrolyte levels) that you need specialized equipment to identify. Even in these cases, the danger of the battery exploding in the non-professionals face is very high.
Car batteries function via a complex set of chemical reactions triggered by a process known as electrolysis, which creates a DC current between two chemicals that would otherwise not spontaneously react. One of the side effects of electrolysis is a buildup of hydrogen gas, but this gas is normally released from small vents in the battery. However, sometimes these vents get clogged up, which creates the equivalent to a pressurized bomb underneath your hood. In the situation of the W202, the electrolysis was causing an excessive amount of hydrogen gas buildup, and thus the vents could not release it quickly enough.
Again, this is a serious situation that should not be handled by an amateur car enthusiast. The dangers to both your person and your vehicle are significant, and so we highly recommend that you take your W202 to a local Mercedes-Benz maintenance technician who can safely return your car to its former glory.
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